The anterolateral ligament is a secondary stabilizer in the knee joint: A validated computational model of the biomechanical effects of a deficient anterior cruciate ligament and anterolateral ligament on knee joint kinematics

Anterolateral knee complex considerations in contemporary anterior cruciate ligament reconstruction and total knee arthroplasty: a systematic review

The anterolateral ligament (ALL) was first described in 1879 in the context of Segond fractures, which correlate with a 75-100% chance of an anterior cruciate ligament (ACL) tear or a 66-75% chance of a meniscal tear. The purpose of this paper is to provide an updated comprehensive review on the anterolateral ligament complex of the knee focusing on the: (1) anatomy of the ALL/ALC; (2) associated biomechanics/function; and (3) important surgical considerations in contemporary anterior cruciate ligament (ACL) reconstruction and total knee arthroplasty (TKA). A systematic review of studies on ALL was conducted on Pubmed/MEDLINE and Cochrane databases (May 7th, 2020 to February 1st, 2022), with 20 studies meeting inclusion/exclusion criteria. Studies meeting inclusion criteria were anatomical/biomechanical studies assessing ALL function, cadaveric and computer simulations, and comparative studies on surgical outcomes of ALLR (concomitant with ACL reconstruction). Eight studies were included and graded by MINOR and Newcastle-Ottawa scale to identify potential biases. The anatomy of the ALL is part of the anterolateral ligament complex (ALC), which includes the superficial/deep iliotibial band (including the Kaplan fiber system), iliopatellar band, ALL, and anterolateral capsule. Multiple biomechanical studies have characterized the ALC as a secondary passive stabilizer in resisting tibial internal rotation. Given the role of the ALC in resisting internal tibial rotation, lateral extra-articular procedures including ALL augmentation may be considered for chronic ACL tears, ACL revisions, and a high-grade pivot shift test. In the context of TKA, in the event of injury to the ALC, a more constrained implant or soft-tissue reconstruction may be necessary to restore appropriate knee stability.

Modified Lemaire Lateral Extra-articular Tenodesis With the Iliotibial Band Strip Fixed on the Femoral Cortical Surface Reduces Laxity and Causes Less Overconstraint in the Anterolateral Lesioned Knee: A Biomechanical Study

PURPOSE

To compare the biomechanical effects of femoral cortical surface fixation and intra-tunnel fixation in modified Lemaire tenodesis on the restoration of native kinematics in anterolateral structure-deficient knees.

METHODS

Eight fresh-frozen cadaveric knees were mounted in a knee-customized jig to evaluate anterior translation in anterior load and internal rotation degree in internal rotation torque at 0°, 30°, 60°, and 90°, as well as anterolateral translation (ALT) in a simulated pivot-shift test at 0°, 15°, 30°, and 45°. Kinematic tests were performed in the following states: intact; anterolateral knee lesion (AL-Les); modified Lemaire lateral extra-articular tenodesis (LET) with the femoral iliotibial band (ITB) strip fixed on the cortical surface (cortical fixation), deep to the lateral collateral ligament (LCL) (deep LET-C); and LET with the femoral ITB strip fixed into a tunnel (intra-tunnel fixation), deep to the LCL (deep LET-IT) or superficial to the LCL (superficial LET-IT). The knee kinematic changes in the AL-Les state and the 3 LET states were compared with each other, with the intact state as the baseline.

RESULTS

In the AL-Les state, the increased anterior translation instabilities were significantly mitigated by the 3 LETs at 30°, 60°, and 90° (all P < .001), with overconstraint observed in both the deep LET-IT and superficial LET-IT states at 60° (P = .047 and P < .001, respectively) and 90° (both P < .001). Similarly, the 3 LETs significantly reduced the internal rotation instabilities in the AL-Les state at all flexion angles. The superficial LET-IT state overconstrained the knee at 60° (P = .009) and 90° (P < .001) during internal rotation torque, and the deep LET-IT state did so at 60° (P = .012). Furthermore, the ALT instabilities found in the AL-Les state were significantly reduced by the 3 LETs during the simulated pivot-shift test. At 30° and 45°, these LET states resulted in overconstraint when compared with the intact state, but the superficial LET-IT state (P < .001) or deep LET-IT state (P = .016) presented a larger overconstraint than that in the deep LET-C at 45°, respectively.

CONCLUSIONS

The 3 Lemaire LET procedures evaluated reduced the anterior, internal rotational, and ALT laxities in AL-Les knees and restored these parameters to the native baseline of the intact state at most flexion angles. However, in deep flexion, some overconstraint occurred in all LETs when compared with the intact state, of which the deep LET-C state resulted in less overconstraint in anterior translation and internal rotation than the deep LET-IT and superficial LET-IT states.

CLINICAL RELEVANCE

This biomechanical study supports using the femoral cortical fixation technique to fix the ITB strip in the modified Lemaire LET, which similarly improves knee kinematic stability and causes less overconstraint compared with conventional intra-tunnel fixation. These findings need more verification in clinical scenarios.

Computational analysis of tibial slope adjustment with fixed-bearing medial unicompartmental knee arthroplasty in ACL- and PCL-deficient models

AIMS

A functional anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) has been assumed to be required for patients undergoing unicompartmental knee arthroplasty (UKA). However, this assumption has not been thoroughly tested. Therefore, this study aimed to assess the biomechanical effects exerted by cruciate ligament-deficient knees with medial UKAs regarding different posterior tibial slopes.

METHODS

ACL- or PCL-deficient models with posterior tibial slopes of 1°, 3°, 5°, 7°, and 9° were developed and compared to intact models. The kinematics and contact stresses on the tibiofemoral joint were evaluated under gait cycle loading conditions.

RESULTS

Anterior translation increased in ACL-deficient UKA cases compared with intact models. In contrast, posterior translation increased in PCL-deficient UKA cases compared with intact models. As the posterior tibial slope increased, anterior translation of ACL-deficient UKA increased significantly in the stance phase, and posterior translation of PCL-deficient UKA increased significantly in the swing phase. Furthermore, as the posterior tibial slope increased, contact stress on the other compartment increased in cruciate ligament-deficient UKAs compared with intact UKAs.

CONCLUSION

Fixed-bearing medial UKA is a viable treatment option for patients with cruciate ligament deficiency, providing a less invasive procedure and allowing patient-specific kinematics to adjust posterior tibial slope. Patient selection is important, and while AP kinematics can be compensated for by posterior tibial slope adjustment, rotational stability is a prerequisite for this approach. ACL- or PCL-deficient UKA that adjusts the posterior tibial slope might be an alternative treatment option for a skilled surgeon. Cite this article: Bone Joint Res 2022;11(7):494-502.

Anatomy, Biomechanics, and Reconstruction of the Anterolateral Ligament of the Knee Joint

Despite remarkable advances in the clinical outcomes after anterior cruciate ligament reconstructions (ACLRs), residual rotational instability of the knee joint remains a major concern. Since the anterolateral ligament (ALL) on the knee joint has been “rediscovered”, the role of anterolateral structures, including ALL and deep iliotibial band, as secondary stabilizers of anterolateral rotatory instability has gained interest. This interest has led to the resurgence of anterolateral procedures combined with ACLRs to restore rotational stability in patients with anterior cruciate ligament (ACL) deficiencies. However, the difference in concepts between anterolateral ligament reconstructions (ALLRs) as anatomical reconstruction and lateral extra-articular tenodesis (LETs) as non-anatomical reinforcement has been conflicting in present literature. This study aimed to review the anatomy and biomechanics of anterolateral structures, surgical techniques, and the clinical outcomes of anterolateral procedures, including LET and ALLR, in patients with ACL deficiencies.

Effects of the Anterolateral Ligament and Anterior Cruciate Ligament on Knee Joint Mechanics: A Biomechanical Study Using Computational Modeling

Background:

Recent studies on lateral knee anatomy have reported the presence of a true ligament structure, the anterolateral ligament (ALL), in the anterolateral region of the knee joint. However, its biomechanical effects have not been fully elucidated.

Purpose:

To investigate, by using computer simulation, the association between the ALL and anterior cruciate ligament (ACL) under dynamic loading conditions.

Study Design:

Descriptive laboratory study; Level of evidence, 5.

Methods:

The authors combined medical imaging from 5 healthy participants with motion capture to create participant-specific knee models that simulated the entire 12 degrees of freedom of tibiofemoral (TF) and patellofemoral (PF) joint behaviors. These dynamic computational models were validated using electromyographic data, muscle activation data, and data from previous experimental studies. Forces exerted on the ALL with ACL deficiency and on the ACL with ALL deficiency, as well as TF and PF contact forces with deficiencies of the ACL, ALL, and the entire ligament structure, were evaluated under gait and squat loading. A single gait cycle and squat cycle were divided into 11 time points (periods 0.0-1.0). Simulated ligament forces and contact forces were compared using nonparametric repeated-measures Friedman tests.

Results:

Force exerted on the ALL significantly increased with ACL deficiency under both gait- and squat-loading conditions. With ACL deficiency, the mean force on the ALL increased by 129.7% under gait loading in the 0.4 period ( P < .05) and increased by 189% under high flexion during the entire cycle of squat loading ( P < .05). A similar trend of significantly increased force on the ACL was observed with ALL deficiency. Contact forces on the TF and PF joints with deficiencies of the ACL, ALL, and entire ligament structure showed a complicated pattern. However, contact force exerted on TF and PF joints with respect to deficiencies of ACL and ALL significantly increased under both gait- and squat-loading conditions.

Conclusion:

The results of this computer simulation study indicate that the ACL and the ALL of the lateral knee joint act as secondary stabilizers to each other under dynamic load conditions.

Tibiofemoral contact and alignment in patients with anterior cruciate ligament rupture treated nonoperatively versus reconstruction : an upright, open MRI study

AIMS

Anterior cruciate ligament (ACL) rupture commonly leads to post-traumatic osteoarthritis, regardless of surgical reconstruction. This study uses standing MRI to investigate changes in contact area, contact centroid location, and tibiofemoral alignment between ACL-injured knees and healthy controls, to examine the effect of ACL reconstruction on these parameters.

METHODS

An upright, open MRI was used to directly measure tibiofemoral contact area, centroid location, and alignment in 18 individuals with unilateral ACL rupture within the last five years. Eight participants had been treated nonoperatively and ten had ACL reconstruction performed within one year of injury. All participants were high-functioning and had returned to sport or recreational activities. Healthy contralateral knees served as controls. Participants were imaged in a standing posture with knees fully extended.

RESULTS

Participants' mean age was 28.4 years (SD 7.3), the mean time since injury was 2.7 years (SD 1.6), and the mean International Knee Documentation Subjective Knee Form score was 84.4 (SD 13.5). ACL injury was associated with a 10% increase (p = 0.001) in contact area, controlling for compartment, sex, posture, age, body mass, and time since injury. ACL injury was associated with a 5.2% more posteriorly translated medial centroid (p = 0.001), equivalent to a 2.6 mm posterior translation on a representative tibia with mean posteroanterior width of 49.4 mm. Relative to the femur, the tibiae of ACL ruptured knees were 2.3 mm more anteriorly translated (p = 0.003) and 2.6° less externally rotated (p = 0.010) than healthy controls. ACL reconstruction was not associated with an improvement in any measure.

CONCLUSION

ACL rupture was associated with an increased contact area, posteriorly translated medial centroid, anterior tibial translation, and reduced tibial external rotation in full extension. These changes were present 2.7 years post-injury regardless of ACL reconstruction status. Cite this article: Bone Joint J 2021;103-B(9):1505-1513.

MRI Evaluation of Anterolateral Ligament of the Knee: A Cross-Sectional Study in Malaysia

Introduction After detailed anatomical delineation of the anterolateral ligament (ALL) of the knee, there is a surge in research on this anatomical structure. Owing to the anatomical variation and lack of experience in the identification of this structure, magnetic resonance (MR) evaluation of the ALL produces mixed results. It was aimed to evaluate the ALL using the routinely performed MR imaging of the knee and to determine any associated factors with ALL injuries. Materials and methods Thirty-six MR images of the knee from 31 patients from January 1, 2017, to June 30, 2017, are evaluated. MR sequences performed include T1-weighted, T2-weighted, proton density (PD), and PD fat saturation (FS). All MR images were double-read by two authors and approved by a consultant radiologist with more than 20 years of radiological experience. The ALL was divided into three portions: femoral, meniscal, and tibial, and the ALL was considered fully visualized when all three portions were seen on MR images. Results At least a portion of the ALL was visualized in 27 scans (75%), and it was fully visualized in 20 scans (55.6%). The femoral portion was the most commonly identified (75%), followed by the meniscal portion (69.4%) and the tibial portion (58.3%). ALLs were best visualized on coronal view in PD FS with the lateral inferior genicular artery as a guide to locate the bifurcation of the meniscal and tibial components. Conclusion The ALL can be visualized in routine 1.5-T MR imaging, either full delineation (55.6%) or partially visualized (75%). It is best characterized via a PD-weighted sequence with fat saturation on the coronal plane. The ALL injury was associated with an anterior cruciate ligament (ACL) injury.

Editorial Commentary: Knee Anterolateral Ligament Cadaveric, Biomechanical Analysis Should Include Tensioning of All Knee Dynamic Structures

Although most reports in the literature suggest that the knee anterolateral structures contribute to the anterolateral rotational stability of the knee, the extent of its contribution is still controversial. There are many dynamic structures that also affect the stability of the knee joint, including the iliotibial band and quadriceps muscle. Although not all of the dynamic structures surrounding the knee influence stability associated with the anterior cruciate ligament, we recommend that cadaveric, biomechanical analysis of the knee anterolateral ligament and related structures include tensioning of all knee dynamic structures to avoid potential biases.

The extensor efficiency of unicompartmental, bicompartmental, and total knee arthroplasty

Aims

Unicompartmental knee arthroplasty (UKA) and bicompartmental knee arthroplasty (BCA) have been associated with improved functional outcomes compared to total knee arthroplasty (TKA) in suitable patients, although the reason is poorly understood. The aim of this study was to measure how the different arthroplasties affect knee extensor function.

Methods

Extensor function was measured for 16 cadaveric knees and then retested following the different arthroplasties. Eight knees underwent medial UKA then BCA, then posterior-cruciate retaining TKA, and eight underwent the lateral equivalents then TKA. Extensor efficiency was calculated for ranges of knee flexion associated with common activities of daily living. Data were analyzed with repeated measures analysis of variance (α = 0.05).

Results

Compared to native, there were no reductions in either extension moment or efficiency following UKA. Conversion to BCA resulted in a small decrease in extension moment between 70° and 90° flexion (p < 0.05), but when examined in the context of daily activity ranges of flexion, extensor efficiency was largely unaffected. Following TKA, large decreases in extension moment were measured at low knee flexion angles (p < 0.05), resulting in 12% to 43% reductions in extensor efficiency for the daily activity ranges.

Conclusion

This cadaveric study found that TKA resulted in inferior extensor function compared to UKA and BCA. This may, in part, help explain the reported differences in function and satisfaction differences between partial and total knee arthroplasty.

Cite this article: Bone Joint Res 2021;10(1):1–9.

The importance of plasmin for the healing of the anterior cruciate ligament

Aims

The anterior cruciate ligament (ACL) is known to have a poor wound healing capacity, whereas other ligaments outside of the knee joint capsule such as the medial collateral ligament (MCL) apparently heal more easily. Plasmin has been identified as a major component in the synovial fluid that varies among patients. The aim of this study was to test whether plasmin, a component of synovial fluid, could be a main factor responsible for the poor wound healing capacity of the ACL.

Methods

The effects of increasing concentrations of plasmin (0, 0.1, 1, 10, and 50 µg/ml) onto the wound closing speed (WCS) of primary ACL-derived ligamentocytes (ACL-LCs) were tested using wound scratch assay and time-lapse phase-contrast microscopy. Additionally, relative expression changes (quantitative PCR (qPCR)) of major LC-relevant genes and catabolic genes were investigated. The positive controls were 10% fetal calf serum (FCS) and platelet-derived growth factor (PDGF).

Results

WCS did not differ significantly among no plasmin versus each of the tested concentrations (six donors). The positive controls with PDGF and with FCS differed significantly from the negative controls. However, we found a trend demonstrating that higher plasmin concentrations up-regulate the expression of matrix metalloproteinase 13 (MMP13), 3 (MMP3), and tenomodulin (TNMD).

Conclusion

The clinical relevance of this study is the possibility that it is not solely the plasmin, but also additional factors in the synovial fluid of the knee, that may be responsible for the poor healing capacity of the ACL.

Cite this article: Bone Joint Res 2020;9(9):543–553.

Restoration of normal knee kinematics with respect to tibial insert design in mobile bearing lateral unicompartmental arthroplasty using computational simulation

Aims

Mobile-bearing unicompartmental knee arthroplasty (UKA) with a flat tibial plateau has not performed well in the lateral compartment, leading to a high rate of dislocation. For this reason, the Domed Lateral UKA with a biconcave bearing was developed. However, medial and lateral tibial plateaus have asymmetric anatomical geometries, with a slightly dished medial and a convex lateral plateau. Therefore, the aim of this study was to evaluate the extent at which the normal knee kinematics were restored with different tibial insert designs using computational simulation.

Methods

We developed three different tibial inserts having flat, conforming, and anatomy-mimetic superior surfaces, whereas the inferior surface in all was designed to be concave to prevent dislocation. Kinematics from four male subjects and one female subject were compared under deep knee bend activity.

Results

The conforming design showed significantly different kinematics in femoral rollback and internal rotation compared to that of the intact knee. The flat design showed significantly different kinematics in femoral rotation during high flexion. The anatomy-mimetic design preserved normal knee kinematics in femoral rollback and internal rotation.

Conclusion

The anatomy-mimetic design in lateral mobile UKA demonstrated restoration of normal knee kinematics. Such design may allow achievement of the long sought normal knee characteristics post-lateral mobile UKA. However, further in vivo and clinical studies are required to determine whether this design can truly achieve a more normal feeling of the knee and improved patient satisfaction.

Cite this article: Bone Joint Res 2020;9(7):421–428.

Decellularized porcine xenograft for anterior cruciate ligament reconstruction: A histological study in sheep comparing cross-pin and cortical suspensory femoral fixation

Aims

To evaluate graft healing of decellularized porcine superflexor tendon (pSFT) xenograft in an ovine anterior cruciate ligament (ACL) reconstruction model using two femoral fixation devices. Also, to determine if pSFT allows functional recovery of gait as compared with the preoperative measurements.

Methods

A total of 12 sheep underwent unilateral single-bundle ACL reconstruction using pSFT. Two femoral fixation devices were investigated: Group 1 (n = 6) used cortical suspensory fixation (Endobutton CL) and Group 2 (n = 6) used cross-pin fixation (Stratis ST). A soft screw was used for tibial fixation. Functional recovery was quantified using force plate analysis at weeks 5, 8, and 11. The sheep were euthanized after 12 weeks and comprehensive histological analysis characterized graft healing at the graft-bone interface and the intra-articular graft (ligamentization).

Results

The pSFT remodelled into a ligament-like structure and no adverse inflammatory reaction was seen. The ground reaction force in the operated leg of the Endobutton group was higher at 11 weeks (p < 0.05). An indirect insertion was seen at the graft-bone interface characterized by Sharpey-like fibres. Qualitative differences in tendon remodelling were seen between the two groups, with greater crimp-like organization and more aligned collagen fibres seen with Endobutton fixation. One graft rupture occurred in the cross-pin group, which histologically showed low collagen organization.

Conclusion

Decellularized pSFT xenograft remodels into a ligament-like structure after 12 weeks and regenerates an indirect-type insertion with Sharpey-like fibres. No adverse inflammatory reaction was observed. Cortical suspensory femoral fixation was associated with more enhanced graft remodelling and earlier functional recovery when compared with the stiffer cross-pin fixation.