Lateral Meniscus Posterior Root Research Articles

Lateral meniscus root tear in anterior cruciate ligament injured patients is not associated with increased rotatory knee laxity: A quantitative pivot shift analysis

ObjectivesBiomechanical investigations conducted in vitro have elucidated the detrimental impact of lateral meniscus posterior root (LMPR) tears on knee contact pressures in the anterior cruciate ligament (ACL)-injured knee. Nevertheless, the influence of LMPR tears on the kinematics of ACL-injured patients remains ambiguous. The purpose of this study was to assess the impact of LMPR tears on anteroposterior and rotatory knee laxity employing a clinically validated quantitative pivot shift (QPS) analysis system. MethodsPatients with ACL injury recruited in a prospective ACL registry spanning from 2012 to 2020 were retrospectively screened for eligibility. Criteria for inclusion encompassed complete primary ACL tears, absence of concurrent ligamentous or osseous injuries requiring operative treatment, and no prior knee surgeries.Patients were assigned to two cohorts based on the presence (LMPR+) or absence (LMPR-) of an LMPR tear concomitant with ACL injury. Each patient underwent a standardized PS test, measurement of anterior tibial translation (ATT) (mm) using the Rolimeter, and QPS (mm) with a tablet-based image analysis system (PIVOT App). Comparative analyses of categorical variables were performed using the Fisher exact and Chi-square tests, while non-normally distributed continuous variables were compared between groups with the Mann–Whitney U test. Alfa was set at 0.05. ResultsA total of 99 patients were included in the study, of which 22 were assigned to the LMPR+ and 77 to the LMPR- group. Tear depth was considered partial in 13 (59%) patients and full in 9 (41%) patients. The prevalence of medial meniscus tears was greater in the LMPR+ (n ​= ​16, 73%) compared with the LMPR- (n ​= ​33, 43%) group (p ​= ​0.01). No difference was observed in ATT measured with the Rolimeter (p ​= ​0.63). Similarly, no difference was found in QPS between the LMPR+ (2.3 ​mm) and the LMPR- (1.9 ​mm) group (p ​= ​0.08). ConclusionUtilizing QPS in this investigation, LMPR tears do not significantly increase ATT or rotatory knee laxity. Consequently, although repairing LMRT associated with ACL injuries may be advisable for minimizing joint stress, their impact on controlling the PS in patients remains uncertain. Level of evidenceIII, retrospective comparative study.

Intra-Tunnel Knotless Anchor Fixation for Lateral Meniscus Posterior Root Tears: A Novel Technique.

Lateral meniscus posterior root tears (LMPRTs) are radial tears that occur within 10mm of the posterior root tibial connection, also known as lateral meniscus posterior root avulsions. A common surgical approach for LMPRT (2) that contributes to positive biomechanical outcomes is independent transtibial pullout repair.(6,7,8) If this treatment is performed on people who need both LMPRT repair and ACL restoration, an extra tibial tunnel is required. The installation of a tibial tunnel increases surgical challenges and lengthens operation time, as well as the danger of iatrogenic damage to the normal architecture of the knee. To circumvent these drawbacks, we have developed a novel technique for intra-tunnel LMPRT repair using a knotless anchor construct at the upper posterior edge of the tibial tunnel. A stab incision is made to create the standard antero lateral portal and after introducing the trochar and the scope, a round of diagnostic arthroscopy is performed and the posterior root of lateral meniscus tear is identified. After creating an anteromedial portal, With help of 1 fiber tape, a loaded bite is taken with the help of a first pass mini device (Smith & Nephew), via the antero medial portal, deep into the posterior root ( around 5mm), using a self winching technique, and reduction of the LMPRT is checked. The position for the anchor entry is visualized in the superior edge of the tibial tunnel along its posterior wall, and the tapes are passed through the knotless anchor extra-articulately outside the AM portal. Thereafter, the anchor is shuttled in through the AM portal and punched in the footprint on the posterior-superior edge of the tibial tunnel with visualization of the reduction of the LMPR to the footprint. This technique offers a simple solution to a complex problem in the form of a simple procedure. This technique is a good choice when a tear of the posterior root of the LM occurs.

Evaluation of the Outcomes of Combined Lateral Meniscus Posterior Root and Anterior Cruciate Ligament Reconstruction

Evaluation of the Outcomes of Combined Lateral Meniscus Posterior Root and Anterior Cruciate Ligament Reconstruction

Male Sex, Revision Surgery, Low Volume of Anterior Cruciate Ligament Remnant, and Significant Instability Are Risk Factors for Posterior Root Tear of the Lateral Meniscus in Patients Undergoing Anterior Cruciate Ligament Reconstruction

PurposeThis multicenter study aimed to determine the incidence of lateral meniscus posterior root tears (LMPRTs) in patients undergoing ACL reconstruction and identify associated risk factors. MethodsWe conducted a retrospective, multicenter study using data from the Francophone Arthroscopic Society's registry. The study included all the patients in the registry who underwent ACL reconstruction surgery between June 2020 and June 2023, we excluded incomplete data. We compared delay from injury to surgery between LMPRTs group and No LMPRTs group. Variables investigated as potential risk factors for LMPRTs included age, sex, nature of surgery (primary or revision), pivot shift test result, side-to-side laxity under anesthesia, presence of ACL remnant, occurrence of medial meniscal tear, and presence of collateral ligament injury. Risk factors were analyzed using a logistic regression model. ResultsAmong the 5359 patients analyzed, LMPRTs occurred in 7.0% (n=375) of cases during ACL reconstruction. Mean age at surgery was 29.3 +/- 10.3 years old [11-77]. Concerning delay to surgery, the mean time was 8.4 +/- 23.1 weeks [0.0-347.2] in the No LMPRTs group and 6.5 +/- 10.2 weeks [0.2-61.6] in the LMPRTs group (p = 0.109). Univariate analysis revealed that male sex (p < 0.001), revision surgery (p < 0.001), medial meniscal injury (p = 0.007), ACL remnant (0% vs > 70%, <10% vs > 70%, 10 to 30% vs > 70%, 30 to 50% vs > 70%, 50 to 70% vs > 70%; p < 0.001) and higher pivot shift grade (p = 0.011) were significantly associated with a presence of LMPRTs. Age, side-to-side laxity, and collateral ligament injury were not found to be significant risk factor In multivariate analysis : male sex, revision surgery, pivot shift test result and a low volume of ACL remnant remained significant. Side to side laxity was also a significant factor in multivariate analysis. ConclusionThis study identified male sex, revision surgery, low volume of ACL remnant, side to side laxity and higher grade of pivot shift as significant risk factors for LMPRTs during ACL reconstruction.

Association of Increased Lateral Femoral Condylar Ratio With Lateral Meniscus Posterior Root Tear in Noncontact ACL Injury.

In the setting of anterior cruciate ligament (ACL) injury, lateral meniscus posterior root tears (LMPRTs) are less readily diagnosed on preoperative magnetic resonance imaging (MRI). Therefore, to predict LMPRTs in ACL injuries, it is necessary to understand the risk factors associated with them. The purpose of this study was to investigate the association of lateral femoral condylar ratio (LFCR) with LMPRTs in ACL injuries. It was hypothesized that an increased LFCR would be associated with LMPRTs in noncontact ACL injuries. Cohort study; Level of evidence, 3. Enrolled were consecutive patients who underwent primary acute (<6 weeks from injury) ACL reconstruction after noncontact injury and had LMPRT confirmed on preoperative MRI and arthroscopically (combined group; n = 62) as well as patients who underwent isolated acute ACL reconstruction (isolated group; n = 80) who were matched to the combined group by age, height, and body mass index (BMI). All patients underwent surgery between January 1999 and November 2021. LFCR and posterior tibial slope (PTS) were measured and compared between the isolated and combined groups. The area under the receiver operating characteristic curve (AUC) was calculated to determine the cutoff for detecting increased risk of LMPRTs. The demographic characteristics of the 2 groups did not differ significantly, nor did the PTS. The LFCR was a significant factor (odds ratio [OR], 1.23; P = .001) associated with LMPRT. Patient age, height, BMI, and PTS were not associated with LMPRT. The AUC (0.66; 95% CI, 0.57-0.75) for LFCR had a sensitivity of 39% and specificity of 90% to predict LMPRT. The calculated cutoff associated with an increased risk for LMPRT when compared with the isolated group was 67.0% (OR, 4.98; 95% CI, 2.10-11.79). Increased LFCR was associated with the presence of LMPRTs in patients with acute ACL injuries. The LFCR may provide surgeons with additional information regarding the risk of having a concomitant LMPRT when planning ACL reconstructions.

Increased Posterior Tibial Slope Is Associated With Increased Risk of Meniscal Root Tears: A Systematic Review

Background: While increased posterior tibial slope (PTS) is an established risk factor for anterior cruciate ligament tears, the association between tibial slope and meniscal posterior root tears is not well-defined. Purpose: To summarize the available literature evaluating the association between PTS and meniscus root injuries compared with patients without root tears. Study Design: Systematic review; Level of evidence, 4. Methods: A literature search was performed using the Scopus, PubMed, and Embase databases. Human clinical studies evaluating the associations between the medial tibial slope (MTS), lateral tibial slope (LTS), lateral-to-medial (L-to-M) slope asymmetry, and the risk of meniscus root tears were included. Patients with medial meniscus posterior root tears (MMPRTs) and lateral meniscus posterior root tears (LMPRTs) were compared with a control group without root injury. Study quality was assessed using the methodological index for non-randomized studies criteria. Results: Ten studies with 1313 patients were included (884 patients with root tears; 429 controls). The LMPRT subgroup (n = 284) had a significantly greater LTS (mean ± SD, 7.3°± 1.5° vs 5.7°± 3.91°; P < .001), MTS (5.26°± 1.2° vs 4.8°± 1.25°; P < .001), and increased L-to-M asymmetry (2.3°± 1.3° vs 0.65°± 0.5°; P < .001) compared with controls. The MMPRT group (n = 600) had significantly increased MTS relative to controls (8.1°± 2.5° vs 4.3°± 0.7°; P < .001). Furthermore, there was a higher incidence of noncontact injuries (79.3%) and concomitant ramp lesions (56%) reported in patients with LMPRT. Conclusion: Increased MTS, LTS, and L-to-M slope asymmetry are associated with an increased risk of LMPRTs, while increased MTS is associated with MMPRTs. Surgeons should consider how proximal tibial anatomy increases the risk of meniscus root injury.

Arthroscopic Lateral Meniscus Root Repair With Reverse Suture Anchor Technique

The stability of the knee joint is crucially dependent on the integrity of the lateral meniscus posterior root, which is often accompanied by anterior cruciate ligament injury. Anchor suture repair for lateral meniscus posterior root injury not only achieves better biomechanical effects but also ensures favorable prognosis. However, the placement of anchors often requires the establishment of a posterior approach, and the insertion of an anchor is a technical challenge. In light of this, we have applied the technique of reverse anchor fixation for repairing the lateral meniscus posterior root, which not only simplifies the procedure but also effectively reduces the “bungee effect.”

How To Avoid Suture Damage in Simultaneous Anterior Cruciate Ligament Reconstruction and Lateral Meniscal Posterior Root Reinsertion With the Transtibial Pullout Technique: A Technical Note

Lateral meniscus posterior root tears (LMPRTs) are estimated to occur in 7% to 12% of anterior cruciate ligament (ACL)-injured knees. This topic is of great interest because of their biomechanical consequences in terms of interruption of hoop stress distribution. If left unrepaired, the corresponding compartment is exposed to unfavorable contact dynamics, similar to those resulting from a total meniscectomy. This Technical Note describes a transtibial LMPRT repair using a Knee Scorpion and an 18-gauge spinal needle. It is a reproducible arthroscopic LMPR reinsertion technique combined with concomitant standard ACL + anterolateral ligament reconstruction with hamstring tendons and it describes how to safely avoid damage to root traction sutures during the ACL independent tibial tunnel drilling.

The Risk of Iatrogenic Posterior Neurovascular Injuries in Lateral Meniscal Repair Based on the Standard Arthroscopic Knee Position: A Magnetic Resonance Imaging Study.

Repair of the posterior horn of the lateral meniscus using an all-inside meniscal repair device involves the risk of iatrogenic posterior neurovascular injuries. Previous studies that have evaluated this risk were based on preoperative magnetic resonance imaging (MRI) with the knee in 30° of flexion and used landmarks that are impractical in the actual operative situation. To use an MRI model simulating actual knee arthroscopic conditions to (1) compare the potential risk of injuries related to the lateral border of the posterior lateral meniscus root (LMR) through the anterolateral versus anteromedial portal and (2) establish "safe" and "danger" zones to reduce the possibility of injuries to posterior neurovascular structures when performing lateral meniscal repair in relation to the lateral border of the posterior LMR. Descriptive laboratory study. Using 29 axial MRI scans of knees in the figure-of-4 position with joint fluid dilatation at the level of the lateral meniscus, direct lines were drawn to simulate a straight all-inside meniscal repair device deployed from the anterolateral and anteromedial portals to the lateral border of the posterior LMR, extending 14 mm beyond the joint capsule. If the line passed through or touched a posterior neurovascular structure, a risk of iatrogenic injuries was noted, and measurements were made to determine the safe zone in relation to the lateral border of the posterior LMR. Repairing the lateral meniscus through the anterolateral portal in relation to the lateral border of the posterior LMR resulted in a significantly greater risk of posterior neurovascular injuries compared with repairing through the anteromedial portal, with injury incidences of 68.97% and 10.35%, respectively (P = .001). The safe zones of lateral meniscal repair through the anterolateral and anteromedial portals were 4.15 ± 1.87 and 6.57 ± 0.98 mm, respectively, beyond the lateral border of the posterior LMR. The risk of posterior neurovascular injuries when repairing posterior lateral meniscal tissue was found to be significantly greater through the anterolateral portal compared with the anteromedial portal. Surgeons can use the safe zones as defined in this study to decrease the risk of iatrogenic posterior neurovascular injuries during arthroscopic lateral meniscal repair.

Anatomical Double-Row Lateral Meniscus Root Repair Using Suture Anchors

Posterior lateral meniscus root tear leads to extrusion of meniscus and increased instability of knee joint. This leads to loss of hoop stresses with increased and progressive wear of cartilage. Conservative management of root tear in the absence of osteoarthritis is ineffective, and meniscus root repair results in delayed progression of osteoarthritis and improved clinical outcomes. Lateral meniscus root, having a larger surface area, needs a stiffer and secure fixation. Our double-row meniscus root repair technique allows a larger contact area for healing, better biomechanics, low retear, and no tunnel interference with concomitant procedure.

An Improved Transosseous Pullout Suture Technique for Arthroscopic Repair of a Meniscus Root Tear.

This study aimed to explore the clinical efficiency of an improved transosseous pullout suture technique for arthroscopic repair of a meniscus root tear. From January 2017 to January 2021, 53 patients with posterior meniscus root tears combined with anterior cruciate ligament (ACL) and/or posterior cruciate ligament (PCL) tears were collected. Totally, in 29 patients (group A), the 2.0 mm modified pullout tunnel method was used to suture the posterior meniscus root, while 24 patients (group B) were treated with the traditional 4.5 mm pullout tunnel method. In group A, 20 patients had lateral meniscus posterior root (LMPR) combined with ACL tears, 5 patients had LMPR combined with ACL and PCL tears, and 4 patients had medial meniscus posterior root (MMPR) combined with ACL tears. In group B, 19 patients had LMPR combined with ACL tears, 3 patients had LMPR combined with ACL and PCL tears, and 2 patients had MMPR combined with ACL tears. The improvement of the Lysholm and VAS scores and the incidence of complications in group A and group B before the operation, 1 month and 3 months after the operation, and after the final follow-up were compared. Preoperative Lysholm score was 26.0±5.6 in group A and 26.7±5.8 in group B (P>0.05). One-month postoperative Lysholm score was 66.5±5.7 in group A and 54.3±2.4 in group B (P<0.001). Three-month postoperative Lysholm score was 81.1±7.2 in group A and 73.2±9.7 in group B (P<0.05). Lysholm scores after the final follow-up was 90.3±5.6 in group A and 90.0±5.0 in group B (P>0.05). Preoperative VAS score was 6.3±1.4 in group A and 6.3±1.2 in group B (P>0.05). One-month postoperative VAS score was 1.8±0.7 in group A and 2.4±0.9 in group B (P<0.05). Three-month postoperative VAS score was 0.7±0.6 in group A and 0.8±0.6 in group B (P>0.05). VAS score after the final follow-up was 0.2±0.4 in group A and 0.3±0.5 in group B (P>0.05). The improved transosseous pullout suture technique using a smaller 2.0 mm bone tunnel can virtually eliminate the risk of conflict with other bone tunnels and facilitate the management of bone tunnels in multiple ligament injuries, while also diminishing suture abrasion caused by the windshield wiper effect. The technique achieves good clinical efficacy.

Shear stress in the medial meniscus posterior root during daily activities

BackgroundMedial meniscus posterior root (MMPR) tears have been reported to occur in middle-aged patients with minor trauma. However, the injury mechanism of MMPR tears remains unclear. The purpose of this study was to evaluate the shear stress in the MMPR during daily activities using a finite-element analysis. MethodsSubject-specific finite-element models of the knee joint of a healthy middle-aged subject were developed from computed tomographic and magnetic resonance images. A three-dimensional motion capture system “VICON” was used to capture four daily activities: walking, jogging, descending stairs, and landing. The knee joint reaction force was estimated using the AnyBody modeling system. Based on these procedures, the shear stress in the MMPR was calculated during each motion. The shear stress in the lateral meniscus posterior root (LMPR) was also measured to compare the stress between the MMPR and LMPR. ResultsThe shear stress in the MMPR increased as the knee flexion angle increased during each motion. Descending stairs caused more than two-fold greater stress in the MMPR than walking and a similar or greater amount of stress than jogging. The LMPR tended to receive more shear stress than the MMPR throughout each motion. ConclusionsThe present study showed that descending stairs confers almost the same amount of shear stress to the MMPR as jogging. The results of the present study may suggest that descending motion of the knee is an important cause of MMPR tear, and the initiation of descending stairs should be delayed after MMPR repair.

Poster 133: Impact of Popliteal Artery Variation on Sports Medicine Surgery about the Knee

Objectives: Routine, non-contrast knee MRIs were used to assess the prevalence of popliteal artery branching variants. Distances from typical instrumentation in sports medicine operations to the aberrant anteiror tibial artery were measured Methods: A retrospective series of 236 consecutive knee MRIs obtained at a single academic center between March 2022 and May 2022 was compiled. Exclusion criteria included substantial artifact impairing interpretation of the imaging, lesion with mass effect on posterior structures, fracture with significant displacement of the distal femur or tibial plateau, or meniscal injury with displacement of the meniscus. Popliteal artery branching was classified as described by Kim et. al. Measurements were obtained using the imaging software Sectra (Sectra, Linkoping, Sweden). The lateral meniscus was measured in the axial plane at the level of the meniscus. Points representing the posterior-most aspects of the root and posterior horn were selected and these were measured to the popliteal artery. The HTO measurement was performed using the axial plane. A 3D rendering of the MRI was created using the imaging software in Sectra. The axial plane was then reoriented to mimic the oblique cut of the osteotomy. The cut was selected at the level of the proximal extent of the osteotomy just proximal to the fibular head roughly 1.5 cm from the plateau. A point along the posterior tibial cortex closest to the vessel during the procedure was selected as long as it was medial to the lateral most extent of the osteotomy (1 cm from the lateral cortex). The distance from this point to the nearest point of the popliteal artery or its branch was measured. Lastly the proximal tibial tunnel of the posterolateral corner (PLC) reconstruction was measured in the axial plane at a level just above the fibular head. The tunnel was set to have a radius of 5mm to approximate a 10 mm graft tunnel. Statistics were calculated with Excel (Microsoft, Redmond, Washington). Results: 200 patients with 222 knee MRIs were obtained. The average age was 31.5 years, and 51% were male. 48% of images were of the right knee. 92/222 of the knees did not have branching of the anterior tibial artery within the imaging study, which was presumed to represent a distal takeoff. There were 8 (3.6%) of type II popliteal artery variants off which 7 (3.15%) were type IIA-2 with the anterior tibial artery anterior to the popliteus. Amongst the type I anterior tibial arteries, average distance from vessel to lateral meniscus posterior horn and root was 9.7 (+/-2.7) mm and 15.7 (+/-3.0) mm, respectively. The edge of the tibial tunnel for PLC reconstruction was 14.5 (4.0) mm and distance from saw cut of HTO was 7.9 (2.8) mm. For type II-A2, these values were 7.7 (+/-3.0) mm, 11.1 (+/-3.6) mm, 11.8 (+/-4.8) mm, and 0.6 (+/-0.3) mm, respectively. Type II-A2 anterior tibial arteries were signifcantly closer to the lateral meniscus posterior root (p=0.015) and the cut for high tibial osteotomy (p&lt;0.01) when compared to type 1 vessels. Type II-A2 variants were not closer to the posterior horn of the lateral meniscus (p=0.13) or tibial tunnel for PLC reconstruction (p=0.19) when compared to type 1 vessels. Conclusions: Standard MRIs are sufficient for identification of aberrant anterior tibial artery branching patterns and useful for surgical planning around patient specific anatomy. One in thirty patients in our study had proximal type II anterior tibial artery branching anterior to the popliteus. In particular, instrumentation around the proximal poster tibial cortex and lateral meniscus root are at increased risk.This is especially important with the rise of outpatient surgery centers, it is crucial to understand patient-specific anatomy to minimize the risk of vascular injury. [Table: see text][Table: see text]

Lateral Meniscus Extrusion on Magnetic Resonance Imaging of Anterior Cruciate Ligament Injury is Likely Complicated by Lateral Meniscal Posterior Root Tears

Lateral Meniscus Extrusion on Magnetic Resonance Imaging of Anterior Cruciate Ligament Injury is Likely Complicated by Lateral Meniscal Posterior Root Tears

New Considerations in ACL Surgery: When Is Anatomic Reconstruction Not Enough?

➤ Clinicians should be careful to assess for associated injuries including anterolateral complex and medial meniscal ramp lesions or lateral meniscal posterior root tears.➤ Consideration of lateral extra-articular augmentation should be given for patients with >12° of posterior tibial slope.➤ Patients with preoperative knee hyperextension (>5°) or other nonmodifiable risk factors, including high-risk osseous geometry, may benefit from a concomitant anterolateral augmentation procedure to improve rotational stability.➤ Meniscal lesions should be addressed at the time of anterior cruciate ligament reconstruction with meniscal root or ramp repair.

Concomitant Medial and Lateral Meniscus Posterior Horn Root Repair With ACL Reconstruction Using Trans-Tibial Tunnel Technique

Concomitant medial meniscus posterior horn root tears and lateral meniscus posterior horn root tears are rare in occurrence. There is limited literature on the simultaneous repair of medial and lateral meniscus root tears, with ACL reconstruction. We discuss management of concomitant medial meniscus posterior horn root tear (MMPHRT), lateral meniscus posterior horn root tear (LMPHRT), and anterior cruciate ligament (ACL) tear. We highlight the surgical technique in which we perform a repair of both medial and lateral meniscus posterior horn root repairs with ACL reconstruction. We explain the sequence of such a repair to avoid tunnel coalescence.

Posterior Root Tears of the Lateral Meniscus Only Affect Tibiofemoral Contact Forces when the Meniscofemoral Ligament Is Involved: A Cadaveric Study

The objective of this study was to examine the impact of progressive radial tears in the lateral meniscal root on the lateral compartment contact forces and joint surface area through a range of motion of knee and evaluate the role of the meniscofemoral ligament (MFL) in preventing adverse tibiofemoral joint forces. Ten fresh frozen cadaveric knees were tested using 6 experimental conditions (0% lateral meniscal posterior root tear, 25% tear, 50% tear, 75% tear, 100% tear, 100% tear and resection of MFL) at five flexion angles (0°, 30°, 45°, 60°, and 90°) under 100-1,000-N axial load. Contact joint pressure and lateral compartment surface area were measured using Tekscan sensors. Statistical analysis, including descriptive, ANOVA, and post hoc Tukey analysis, was performed. Progressive radial tears of the lateral meniscal root were not associated with an increase in tibiofemoral contact pressure or decrease in lateral compartment surface area. Complete lateral root tear and resection of MFL were associated with increased joint contact pressure (P < .001) at knee flexion angles of 30, 45, 60, and 90° and decreased lateral compartment surface (P < .001) at all knee flexion angles area compared to complete lateral meniscectomy alone. Isolated complete tears of lateral meniscus root and progressive radial tears of the lateral meniscus posterior root were not associated with any change to tibiofemoral contact forces. However, additional resection of the MFL increased contact pressure and decreased lateral compartment surface area.

Role of the Anterior Cruciate Ligament, Anterolateral Complex, and Lateral Meniscus Posterior Root in Anterolateral Rotatory Knee Instability: A Biomechanical Study

Background: Injuries to the anterior cruciate ligament (ACL), Kaplan fibers (KFs), anterolateral capsule/ligament (C/ALL), and lateral meniscus posterior root (LMPR) have been separately linked to anterolateral instability. Purpose: To investigate the contributions of the ACL, KFs, C/ALL, and LMPR to knee stability and to measure instabilities resulting from their injury. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen human knees were tested robotically to determine restraints of knee laxity at 0° to 90° of flexion. An 88-N anterior-posterior force (anterior and posterior tibial translation), 5-N·m internal-external rotation, and 8-N·m valgus-varus torque were imposed and intact kinematics recorded. The kinematics were replayed after sequentially cutting the structures (order varied) to calculate their contributions to stability. Another 10 knees were tested in a kinematics rig with optical tracking to measure instabilities after sequentially cutting the structures across 0° to 100° of flexion. One- and 2-way repeated-measures analyses of variance with Bonferroni correction were used to find significance (P < .05) for the robotic and kinematics tests. Results: The ACL was the primary restraint for anterior tibial translation; other structures were insignificant (<10% contribution). The KFs and C/ALL resisted internal rotation, reaching 44% ± 23% (mean ± SD; P < .01) and 14% ± 13% (P < .05) at 90°. The LMPR resisted valgus but not internal rotation. Anterior tibial translation increased after ACL transection (P < .001) and after cutting the lateral structures from 70° to 100° (P < .05). Pivot-shift loading increased anterolateral rotational instability after ACL transection from 0° to 40° (P < .05) and further after cutting the lateral structures from 0° to 100° (P < .01). Conclusion: The anterolateral complex acts as a functional unit to provide rotatory stability. The ACL is the primary stabilizer for anterior tibial translation. The KFs are the most important internal rotation restraint >30° of flexion. Combined KFs + C/ALL injury substantially increased anterolateral rotational instability while isolated injury of either did not. LMPR deficiency did not cause significant instability with the ACL intact. Clinical Relevance: This study is a comprehensive biomechanical sectioning investigation of the knee stability contributions of the ACL, anterolateral complex, and LMPR and the instability after their transection. The ACL is significant in controlling internal rotation only in extension. In flexion, the KFs are dominant, synergistic with the C/ALL. LMPR tear has an insignificant effect with the ACL intact.

The effects of lateral meniscus posterior root tears or repair with anterior cruciate ligament reconstruction on the pressure of the patellofemoral joint: A biomechanical evaluation.

The aim of our study was to evaluate the effect of tear and repair of the lateral meniscal posterior root (LMPR) on the patellofemoral contact pressure of the knee after anterior cruciate ligament (ACL) reconstructed. This was a descriptive study. Six fresh-frozen cadaveric knees collected by The Third Hospital of Hebei Medical University from January 2019 and January 2022 were placed on a customized testing rig. Patellofemoral contact pressures were measured at 30°, 60°, and 90° of flexion using pressure-sensitive film inserted between the patella and trochlea. The following knee states were tested: ACL reconstruction and intact lateral meniscus, ACL reconstruction, and LMPR tear, and ACL reconstruction and LMPR repair. Pressure measurements were recorded for each state. In the ACL-reconstructed knee, a tear of the LMPR increased patellofemoral contact pressure at 30° of knee flexion. The repair of the posterior root by transosseous pull-out suture reduced the patellofemoral contact pressure as the status of intact lateral meniscal posterior root at 30° of knee flexion. There was no statistical difference between ACL reconstruction with the intact meniscal root and with the meniscal root tear and with the meniscal root repair at 60° and 90° of knee flexion. The posterior root tear and repair of the lateral meniscus could have an influence on patellofemoral contact stress of the knee after ACL reconstruction at 30° of knee flexion.

Lateral-medial asymmetry of posterior tibial slope and small lateral tibial plateau articular surface depth are morphological factors of lateral meniscus posterior root tears in ACL-injured patients.

To investigate whether knee morphological features, patient characteristics, and intraoperative findings are associated with a lateral meniscus (LM) posterior root tear (LMPRT) in anterior cruciate ligament (ACL) injuries with the integrated data from two academic centres. This retrospective study used registry data acquired prospectively at two academic centres. Patients with ACL reconstruction (ACLR) with LMPRT and no other LM injury were selected (LMPRT group) from each database. The control group included patients who underwent ACLR without LM tears. Patients were matched to the LMPRT group according to age and gender (1:1). Morphological factors evaluated on preoperative magnetic resonance image scans included lateral femoral condyle (LFC) anterior-posterior diameter, height, and depth; lateral tibial plateau (LTP) articular surface (AS) depth and sagittal plane depth; and lateral and medial posterior tibial slopes (PTSs). LFC height and depth ratios, LTP AS depth and sagittal plane depth ratios, and lateral-to-medial slope asymmetry were computed from previous measurements. Patient characteristics and intraoperative findings were extracted and compared between both groups. The study included 252 patients (126 in each group). The lateral-medial asymmetry of PTS was greater in the LMPRT group (1.2° vs 0.3°, p < 0.05), and the LTP AS depth was smaller in the LMPRT group (31.4mm vs 33.2mm, p < 0.01). There were no differences in LFC morphology between the control and LMPRT groups. Pivot shift grade (p < 0.05), percentage of complete ACL tears (p < 0.05), and medial meniscus ramp lesions (p < 0.05) were significantly higher in the LMPRT group. LMPRT was associated with significantly increased lateral-medial asymmetry of PTS and significantly smaller LTP AS depth. LMPRT was also associated with an increase in the preoperative pivot shift grade and the presence of a medial meniscus ramp lesion. These morphological characteristics are rather simple to measure and would serve as helpful indicators to preoperatively detect LMPRT, which is frequently challenging to diagnose preoperatively. Level III.