Anatomic and Histological Study of the Anterolateral Aspect of the Knee: A SANTI Group Investigation

Synergistic effect of the anterolateral ligament and capsule injuries on the knee laxity in anterior cruciate ligament injured knees: A cadaveric study

INTRODUCTION

There is much controversy about the practical role of the anterolateral ligament (ALL) and its relation to other anterolateral knee structures including the anterolateral capsule (ALC) and iliotibial band (ITB). The purpose of this cadaveric study was to investigate the effect of the ALL and ALC injuries on knee laxity with the iliotibial band (ITB) preserved in the anterior cruciate ligament (ACL)-injured knee.

HYPOTHESIS

The ALL and ALC would contribute to knee joint stability during anterior translation and internal rotation of the tibia in an ACL-injured knee.

MATERIAL AND METHODS

For 10 fresh-frozen cadaveric knees, we measured knee laxity with the following state of knee injuries with ITB preserved: (1) intact knee, (2) ACL-sectioned knee (ACL-), (3) additional sectioning of the ALL (ACL-/ALL-), and (4) additional sectioning of the ALC (ACL-/ALL-/ALC-). We did biomechanical measurements in internal-external rotation, anterior-posterior translation, and varus-valgus angulation for each condition at knee flexion angles of 0°, 30°, 60°, and 90°.

RESULTS

After we sectioned the ALL (ACL-/ALL-), the mean IR at 0°, 30°, 60°, and 90° of knee flexion were significantly increased, compared to the intact knee (p=<0.001, <0.001, <0.001, and 0.002) and ACL- (p=<0.001, <0.001, <0.001, and 0.002). The additional transection of the ALC (ACL-/ALL-/ALC-) significantly increased IR laxity from the ACL-/ALL- at 30°, 60°, and 90° (p=0.005, 0.003, and 0.047). For anterior laxity, ACL-/ALL- resulted in significantly increased anterior laxity from the ACL- at 30° and 60° (p=0.003 and 0.019), and ACL-/ALL-/ALC- significantly increased anterior laxity even from the ACL-/ALL- at 30° and 60° (p=0.007 and 0.011). For varus laxity, ACL-/ALL- resulted in significantly increased varus laxity from both the intact knee and ACL- at 60° (p=0.004 and 0.007) and 90° (p=<0.001 and<0.001). ACL-/ALL-/ALC- resulted in significantly increased varus from ACL-/ALL- at 60° and 90° (p=<0.001 and 0.003).

CONCLUSION

The anterolateral ligament and anterolateral capsule injuries in ACL-injured knees even with ITB preserved had a synergistic effect on knee laxity in the aspects of internal rotation, anterior translation, and varus angulation.

LEVEL OF EVIDENCE

II, Controlled laboratory study.

The Segond's fracture and the anterolateral ligament

The study of Mullins et al. reasonably explains how the Segond's fracture is probably the most frequent avulsion fracture of the tibia plateau, but it does not challenge the hypothesis of the existence of a discrete ligament (the ALL) strong enough to sometimes pull out its bony insertion as a result of a forced internal rotation and of an ACL failure.

Lateral Extra-articular Tenodesis Reduces Anterior Cruciate Ligament Graft Force and Anterior Tibial Translation in Response to Applied Pivoting and Anterior Drawer Loads

BACKGROUND

The biomechanical effect of lateral extra-articular tenodesis (LET) performed in conjunction with anterior cruciate ligament (ACL) reconstruction (ACLR) on load sharing between the ACL graft and the LET and on knee kinematics is not clear.

PURPOSE/HYPOTHESIS

The purpose was to quantify the effect of LET on (1) forces carried by both the ACL graft and the LET and (2) tibiofemoral kinematics in response to simulated pivot shift and anterior laxity tests. We hypothesized that LET would decrease forces carried by the ACL graft and anterior tibial translation (ATT) in response to simulated pivoting maneuvers and during simulated tests of anterior laxity.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven cadaveric knees (mean age, 39 ± 12 years [range, 28-54 years]; 4 male) were mounted to a robotic manipulator. The robot simulated clinical pivoting maneuvers and tests of anterior laxity: namely, the Lachman and anterior drawer tests. Each knee was assessed in the following states: ACL intact, ACL sectioned, ACL reconstructed (using a bone-patellar tendon-bone autograft), and after performing LET (the modified Lemaire technique after sectioning of the anterolateral ligament and Kaplan fibers). Resultant forces carried by the ACL graft and LET at the peak applied loads were determined via superposition. ATT was determined in response to the applied loads.

RESULTS

With the applied pivoting loads, performing LET decreased ACL graft force up to 80% (44 ± 12 N; P < .001) and decreased ATT of the lateral compartment compared with that of the intact knee up to 7.6 ± 2.9 mm (P < .001). The LET carried up to 91% of the force generated in the ACL graft during isolated ACLR (without LET). For simulated tests of anterior laxity, performing LET decreased ACL graft force by 70% (40 ± 20 N; P = .001) for the anterior drawer test with no significant difference detected for the Lachman test. No differences in ATT were deteced between ACLR with LET and the intact knee on both the Lachman and the anterior drawer tests (P = .409). LET reduced ATT compared with isolated ACLR on the simulated anterior drawer test by 2.4 ± 1.8 mm (P = .032) but not on the simulated Lachman test.

CONCLUSION

In a cadaveric model, LET in combination with ACLR transferred loads from the ACL graft to the LET and reduced ATT with applied pivoting loads and during the simulated anterior drawer test. The effect of LET on ACL graft force and ATT was less pronounced on the simulated Lachman test.

CLINICAL RELEVANCE

LET in addition to ACLR may be a suitable option to offload the ACL graft and to reduce ATT in the lateral compartment to magnitudes less than that of the intact knee with clinical pivoting maneuvers. In contrast, LET did not offload the ACL graft or add to the anterior restraint provided by the ACL graft during the Lachman test.

Outcomes After Isolated Acute Anterior Cruciate Ligament Reconstruction Are Inferior in Patients With an Associated Anterolateral Ligament Injury

BACKGROUND

Isolated reconstruction of the anterior cruciate ligament (ACL) does not reestablish the normal knee biomechanics in cases of associated injuries to the anterolateral structures. Studies evaluating the potential clinical effect of anterolateral ligament (ALL) injury on the treatment of ACL injuries are necessary to validate the findings of biomechanical studies.

PURPOSE

To evaluate the clinical outcomes and failure rate of ACL reconstruction in patients with and without ALL injury diagnosed using magnetic resonance imaging.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A prospective cohort of patients with acute ACL injury was divided into 2 groups based on the presence (ALL group) or absence (no-ALL group) of ALL injury on preoperative magnetic resonance imaging scans. Both groups underwent anatomic reconstruction of the ACL with autologous hamstring tendon grafts. The Lysholm and subjective IKDC scores (International Knee Documentation Committee), KT-1000 arthrometer and pivot-shift test results, reconstruction failure rate, incidence of contralateral ACL injury, presence of associated meniscal injury, and presence of knee hyperextension were evaluated.

RESULTS

A total of 182 patients were evaluated. Postoperative mean ± SD follow-up was 33.6 ± 7.1 and 36.1 ± 8.1 months for the ALL and no-ALL groups, respectively. No significant differences were found between the groups in terms of age, sex, knee hyperextension, duration of injury before reconstruction, follow-up time, or associated meniscal injuries. In the preoperative evaluation, the pivot-shift grade was similar, and the ALL group had worse KT-1000 arthrometer values (7.9 ± 1.2 mm vs 7.2 ± 1.1 mm; P < .001). In the postoperative evaluation, patients in the no-ALL group had a lower reconstruction failure rate (10.2% vs 1.4%; P = .029) and better clinical outcomes according to the IKDC subjective (85.5 ± 10.7 vs 89.1 ± 6.6; P = .035) and Lysholm scores (85.9 ± 10.1 vs 92.0 ± 6.3; P < .001). There was no postoperative difference in the KT-1000 or pivot-shift results.

CONCLUSION

Combined ACL and ALL injuries were associated with significantly less favorable outcomes than were isolated ACL injuries at a minimum follow-up of 2 years after ACL reconstruction. Patients with concomitant ALL injury showed a higher rerupture rate and worse functional scores.

Paediatric knee anterolateral capsule does not contain a distinct ligament: analysis of histology, immunohistochemistry and gene expression

OBJECTIVES

The presence of a discrete ligament within the knee anterolateral capsule (ALC) is controversial. Tendons and ligaments have typical collagens, ultrastructure, transcription factors and proteins. However, these characteristics have not been investigated in paediatric ALC. The purpose of this study was to characterise the paediatric ALC in terms of tissue ultrastructure and cellular expression of ligament markers scleraxis (SCX)-a basic helix-loop-helix transcription factor-and the downstream transmembrane glycoprotein tenomodulin (TNMD), as compared with the paediatric lateral collateral ligament (LCL) and paediatric quadriceps tendon (QT). We hypothesised that, in comparison to the LCL and QT, the ALC would possess poor collagen orientation and reduced SCX and TNMD expression.

METHODS

15 paediatric ALCs (age 6.3±3.3 years), 5 paediatric LCLs (age 3.4±1.3 years) and 5 paediatric QTs (age 2.0±1.2 years) from fresh cadaveric knees were used in this study. Fresh-frozen samples from each region were cryosectioned and then stained with H&E to evaluate collagen alignment and cell morphology. Expression of SCX and TNMD was determined by gene expression analysis and immunohistochemistry.

RESULTS

The histological sections of the paediatric LCL and QT showed well-organised, dense collagenous tissue fibres with elongated fibroblasts, while the ALC showed more random collagen orientation without clear cellular directionality. The aspect ratio of cells in the ALC was significantly lower than that of the LCL and QT (p<0.0001 and p<0.0001, respectively). The normalised distribution curve of the inclination angles of the nuclei in the ALC was more broadly distributed than that of the LCL or QT, indicating random cell alignment in the ALC. SCX immunostaining was apparent in the paediatric LCL within regions of aligned fibres, while the comparatively disorganised structure of the ALC was negative for SCX. The paediatric LCL also stained positive for TNMD, while the ALC was only sparsely positive for this tendon/ligament cell-surface molecule. Relative gene expression of SCX and TNMD were higher in the LCL and QT than in the ALC.

CONCLUSION

In this study, a distinct ligament could not be discerned in the ALC based on histology, immunohistochemistry and gene expression analysis.

LEVEL OF EVIDENCE

Controlled laboratory study.

Ultrastructural Assessment of the Anterolateral Ligament

Background:

The anterolateral ligament (ALL) has been identified as a structure on the lateral side of the knee, but debate exists regarding whether it is a capsular thickening or a ligament.

Hypothesis:

A detailed ultrastructural characterization of the ALL and its ultrastructure collagen arrangement will reveal it more closely resembles ligamentous tissue than joint capsule.

Study Design:

Descriptive laboratory study.

Methods:

Eight paired knee samples from 4 fresh-frozen male cadavers were used for this study. Samples were harvested from the ALL, the joint capsule, and the medial collateral ligament (MCL). All samples were evaluated with light microscopy (LM), transmission electron microscopy (TEM), and variable pressure scanning electron microscopy (VP-SEM). With LM, the 3 tissues were analyzed and their morphology described. With TEM, the ultrastructure and collagen characteristics were quantified and compared among specimens. Then, the 3-dimensional characteristics were compared with VP-SEM.

Results:

Ultrastructure analysis demonstrated similar morphology between the ALL and MCL, with significant differences in these 2 structures as compared with the joint capsule. On LM, the ALL and MCL were characterized by the presence of a dense collagen fiber oriented in the longitudinal and transversal directions of the fiber bundles, while the joint capsule was found to have a more disorganized architecture. On TEM, the collagen fibers of the ALL and MCL demonstrated similar ultrastructural morphology, with both having collagen fibers in parallel, longitudinal alignment. A quantitative analysis was also performed, with the mean (± SD) diameter of fibrils in the ALL and MCL being 80 ± 2.66 nm and 150 ± 3.35 nm, respectively (all P < .001). The VP-SEM highlighted that ALL and MCL morphology demonstrated arrangements of fiber bundles that are densely packed and organized, in contrast to the disorganized fibers of the joint capsule.

Conclusion:

The ALL and MCL have comparable ultrastructures that are distinctly different from the joint capsule, as visualized on LM, TEM, and VP-SEM.

Clinical Relevance:

The ALL should be considered a distinctive structure of the knee, although strictly connected to the surrounding capsule.

Anterolateral ligament injury has a synergic impact on the anterolateral rotatory laxity in acute anterior cruciate ligament-injured knees

PURPOSE

To investigate the prevalence of the anterolateral ligament (ALL) injuries and its role in rotatory laxity in acute anterior cruciate ligament (ACL)-injured knees.

METHODS

Two-hundred and ninety-six consecutive patients with acute ACL injuries were evaluated retrospectively, excluding those with other ligament injury and undetectable path of ALL in MRI. Patients were divided into two groups based on the degree of ACL injury in arthroscopy (complete versus partial group). Logistic regression and discriminant analysis were performed to assess the risk of pivot shift test.

RESULTS

A total of 169 patients were included (128 with complete and 41 with partial ACL rupture). Overall, 106/169 (62.7%) of ALL injuries were characterized, 87/128 (67.9%) in complete group, and 19/41 (46.3%) in partial group. The incidence of pivot shift was 120/128 (93.8%) and 14/41 (34.1%) in the complete and partial groups, respectively. The odds ratio in the pivot shift of combined ALL injury was found as 3.8 (95% CI 1.8-8.4) with the overall ACL injury, but higher as 17.1 (95% CI 3.1-96.4) with partial group. Higher grade of pivot shift showed a greater incidence of injury of ALL. Degree of ACL injury and ALL injury allowed 87.0% of correct classification of subsequent anterolateral rotatory laxity.

CONCLUSION

Injury to the ALL could have a synergetic effect on anterolateral rotatory laxity in acute ACL-injured knee, however, its effect might be minor in case of complete tear. Careful assessment about combined ALL injury should be considered, especially in knees with high-grade pivot shift in acute ACL-injured knees.

LEVEL OF EVIDENCE

Retrospective prognostic study, Level IV.

Biomechanical comparison of anterolateral ligament anatomical reconstruction with a semi-anatomical lateral extra-articular tenodesis. A cadaveric study

BACKGROUND

To compare the biomechanical behavior of an anterolateral ligament (ALL) anatomical reconstruction and a semianatomical lateral extra-articular tenodesis (LET) in the context of an anterior cruciate ligament (ACL) reconstruction combined with an anterolateral lesion.

METHODS

Twelve cadaveric knees were studied using a testing machine to assess the internal tibial rotation and anterior tibial translation across six surgical states: intact knee, ACL lesion, ACL + ALL lesion, ACL isolated reconstruction, ACL + ALL anatomical reconstruction and ACL + LET procedure. ALL and LET grafts were fixed at full knee extension and neutral rotation.

RESULTS

Presented with combined ACL and ALL lesions, isolated ACL reconstruction failed to restore the internal tibial rotation to intact-knee values (P > 0.05 for all angles). The addition of both an ALL reconstruction and LET procedure significantly reduced the internal rotation, restoring the rotation laxity to intact-knee values at 0° and 30° of flexion (P < 0.05) and with a certain level of overconstraint at 60° and 90° (mean 3° ± 2SD). A higher tendency to overconstraint was observed with the LET, but there was no significant difference when comparing the ALL reconstruction with the LET (P > 0.05 for all angles).

CONCLUSIONS

Residual rotational laxity was found after isolated ACL reconstruction in the presence of an anterolateral lesion. The combination of ACL reconstruction with anatomical ALL reconstruction or the LET procedure resulted in restoration to intact-knee values but with a certain degree of overconstraint in higher flexion angles. Both techniques showed optimal biomechanical results with no data supporting the advantage of one over the other.

Editorial Commentary: The Anterolateral Ligament Really Exists, Now Show Me How to Find It

The anterior lateral complex is commonly associated with anterior cruciate ligament (ACL) injury. This has been evident since the description of the Segond fracture and by the use of lateral extra-articular tenodesis for ACL injury. Although lateral extra-articular tenodesis has been mostly given up owing to a preference for anatomic ACL reconstructions, it is gaining interest as an adjunct to ACL reconstruction. To determine the need for an anterolateral procedure we need to be able to identify those patients with deficiency in the anterolateral complex. Magnetic resonance imaging is a widely available tool and is typically obtained for every suspected ACL knee injury. Further detailed descriptions of the anterior lateral complex on magnetic resonance imaging can assist in determining accurate indications for anterolateral procedures.