Function of the medial meniscus in force transmission and stability

10-Year Survival and Clinical Improvement of Meniscal Allograft Transplantation in Early to Moderate Knee Osteoarthritis

BACKGROUND

Meniscal allograft transplantation (MAT) is a viable option for patients experiencing unicompartmental knee pain after total or subtotal meniscectomy. Nonetheless, caution is recommended when suggesting this procedure in the presence of knee osteoarthritis (OA) because of the higher risk of poor survival and outcomes.

PURPOSE/HYPOTHESIS

The purpose was to document the long-term survival of MAT performed as a salvage procedure in patients with knee OA. The hypothesis was that MAT would significantly reduce pain and increase the function of the affected joint at a long-term follow-up compared with the preoperative condition, with a low number of failures and knee replacement surgeries.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 47 patients (37 men and 10 women) with symptomatic knee OA (Kellgren-Lawrence grades 2 or 3) treated with MAT were evaluated at baseline, 5 years, and a minimum 10-year final follow-up (11.1 ± 1 years) using the Lysholm score, the visual analog scale for pain, the Knee injury and Osteoarthritis Outcome Score subscales, and the Tegner score. A total of 44 patients had undergone previous surgeries. Patient satisfaction, revision surgeries, and failures were also recorded.

RESULTS

A statistically significant improvement was observed in all clinical scores from the baseline assessment to the final follow-up. The Lysholm score improved significantly from 46.4 ± 17.2 at the preoperative assessment to 77.7 ± 20.4 at the intermediate follow-up (P < .001), with a significant decrease at the final follow-up (71 ± 23.3; P = .018). A similar trend was reported for the visual analog scale scale for pain, Knee injury and Osteoarthritis Outcome Score, and Tegner score, with no complete recovery to the previous sports activity level. A total of 33 patients required concurrent procedures, such as anterior cruciate ligament reconstructions, osteotomies, and cartilage procedures. Five patients underwent reoperation and were considered surgical failures, while 15 patients presented a clinical condition of <65 of the Lysholm score and were considered clinical failures. Among these, 4 patients were considered both surgical and clinical failures.

CONCLUSION

MAT surgery has proven to be a valid option for improving pain and function even in OA joints (Kellgren-Lawrence grades 2 or 3), yielding satisfactory results despite a worsening clinical outcome in the long-term follow-up. Therefore, based on the data from this study, orthopaedic surgeons may consider recommending MAT as a salvage procedure even in knees affected by early to moderate OA, while advising patients that the need for combined interventions could potentially reduce graft survival.

Reduced physiological extrusion of the medial meniscus in axial load-bearing condition in anterior cruciate ligament deficiency

PURPOSE

In this study, ultrasonography was used to measure medial meniscus (MM) extrusion under weight-bearing and nonweight-bearing conditions in both anterior cruciate ligament (ACL)-deficient and ACL-intact knee groups. This study aimed to determine the possible differences between these groups with an eventual impact on meniscal tears in ACL-deficient knees.

METHODS

A total of 107 patients who underwent ACL reconstructive surgery between June 2022 and April 2023 were enroled. After applying exclusion criteria, 37 patients met the conditions for inclusion in the study and formed the ACL deficiency group (Group D). Of the 141 patients presenting to an outpatient clinic who agreed to have ultrasonography conducted on their nondiscomforting contralateral knee, 37 patients matched for age, sex, hip-knee-ankle angle and body mass index with Group D patients were selected for the ACL intact group (Group I). Ultrasonography was used to measure MM extrusion in weight-bearing and nonweight-bearing conditions for all participants.

RESULTS

Seventy-four patients were included in the study (n = 37 per group). The supine position showed an MM extrusion of 1.2 ± 0.7 mm in Group I and 1.2 ± 0.7 mm in Group D (not significant). In the standing position, MM extrusion measured 2.0 ± 0.6 mm in Group I and 1.3 ± 0.8 mm in Group D. The difference in extrusion (Δextrusion) between the two positions was 0.8 ± 0.6 in Group I and 0.1 ± 0.2 in Group D, with statistical significance (p < 0.01). A consistent reduction in MM extrusion during weight-bearing was observed in patients with ACL deficiency, irrespective of the duration of ACL deficiency, age, sex and BMI.

CONCLUSION

ACL deficiency did not significantly impact MM extrusion during nonweight-bearing conditions; however, less MM extrusion was observed in response to axial loading conditions. These findings indicate altered MM biomechanics due to increased anterior-posterior meniscal motion and rotational instability after ACL injury.

LEVEL OF EVIDENCE

Level III.

The Usefulness of Posterior Shiny Corner Lesions in the Early Diagnosis of Medial Meniscus Posterior Root Tears

INTRODUCTION

 Posterior shiny corner lesions (PSCLs) have been reported to be useful for the early diagnosis of medial meniscus posterior root tears (MMPRTs) in surgical patients. However, the usefulness of PSCLs in outpatients, particularly regarding the optimal timing of magnetic resonance imaging (MRI) examinations after injury, remains unknown. We hypothesized that PSCLs would normally be observed in patients with MMPRTs within one month of injury.

MATERIALS AND METHODS

 This study included 144 patients with knee pain who visited our hospital between January 2021 and May 2023. MRI findings within and after one month were examined. Fisher's exact test was performed for PSCLs, cleft signs, ghost signs, radial tear signs, bone cysts, and medial meniscus extrusion (MME), which are findings used for the diagnosis of MMPRTs. Time-dependent receiver operating characteristic (ROC) curve analysis was performed for each MRI finding. A binomial logistic regression analysis was performed for age, sex, PSCL, ghost sign, and MME.

RESULTS

PSCLs were observed on 82.6% of the MRI scans within one month, but the positivity rate decreased after one month. After one month, a high percentage of patients had cleft signs and ghost signs. The results of a time-dependent ROC curve analysis showed that the PSCL had better diagnostic ability than the cleft sign, ghost sign, radial tear sign, and MME at a relatively early stage. Additionally, the area under the curve (AUC) of PSCL peaks around 35 days and then declines, reaching 0.8 or less around 40 days. On the other hand, the AUC of the cleft sign and ghost sign began to increase around 30 days after injury, and it exceeded 0.8 after approximately 100 days. The results of the binomial logistic regression analysis revealed significant PSCLs and ghost signs. Independent associations between the PSCL, or ghost sign, and the MMPRT were demonstrated.

CONCLUSION

 This study suggests that PSCLs have a superior diagnostic capability for MMPRT during the early stages of injury compared with other MRI findings in outpatients. In particular, PSCLs have a high positivity rate within one month after injury and a high diagnostic capacity up to 40 days after injury.

Usefulness of Probing Sensor Device for Evaluating Meniscal Suture and Scaffold Implantation

Appropriate suture tension is a key factor in successful meniscal repair. This study aimed to clarify the appropriate value of meniscal stabilization with suture repair based on a probing procedure for healthy porcine menisci and a novel meniscal scaffold. After evaluating the reliability of the probing sensor, meniscal vertical tear and partial meniscectomy models were developed, in which suture repair and meniscal scaffold implantation were performed at suture intervals ranging between 20 and 2.5 mm. The residence forces at each interval were evaluated using a probing sensor. Moreover, a tensile test was conducted to evaluate the displacement and presence or absence of gaps. We found that normal and meniscal scaffolds should be fixed within 5 mm of suture interval. The probing residence forces required were at least 1.0 N for vertical tears and 3.0 N for meniscal scaffolds. These findings may be taken into consideration to reduce suture failure following meniscal tear repair and stabilizing meniscal scaffold fixation.

Functional testing following isolated meniscus repair may help to identify patients who need additional physical therapy prior to a return to activity

OBJECTIVES

Functional testing (FT), commonly used to evaluate dynamic knee function and provide objective information about how well a patient, has progressed in rehabilitation following an anterior cruciate ligament (ACL) reconstruction. The purpose of the study was to determine whether a functional test could be used as an assessment tool for return to activity following isolated meniscus repair.

METHODS

The results of FT completed between 80 and 150 days post-operation (representing 4-months post-operative) in isolated meniscal repair patients were analysed for the involved limb, uninvolved limb, and limb symmetry index (LSI). Involved limb performance and LSI on FT were also recorded for a matched cohort of patients who underwent an isolated ACL reconstruction between 151 and 220 days post-operation (representing 6-months post-operative). The meniscus cohort was compared to the ACL cohort.

RESULTS

The meniscus cohort (n ​= ​26) performed well (LSI of 88% or better) on all functional test exercises, including all hop tests. There were patients in the meniscus cohort who did not achieve 90% LSI on the FT at 4 months. There was no statistically significant difference in any of the tests between the meniscus and ACL (n ​= ​39) cohorts.

CONCLUSION

A majority of isolated meniscal repair patients perform well on FT by 4 months post-operatively and similar to patients undergoing isolated ACL reconstruction at 6 months post-operatively. Not all patients performed well on FT at 4 months post-operatively; however so, there may be a role for FT in isolated meniscal repair patients, and those patients may need further physical therapy prior to a return to sports.

LEVEL OF EVIDENCE

III; Retrospective cohort study.

LEVEL OF EVIDENCE

IV.

Temporary meniscus extrusion is caused by cumulative stress from uphill and downhill tasks in healthy volunteers

Purpose

Excessive mechanical stress accumulates and causes knee injury. Meniscal extrusion is a key factor in detecting the reaction to cumulative mechanical stress. The accumulation of stress strongly depends on environmental conditions such as flat ground or uphill/downhill, and accumulates in knee compartments; only a few studies have reported the effects of different environments on lateral and medial meniscus extrusion. This study aimed to investigate the effects of cumulative uphill/downhill stress on the meniscal extrusion in each compartment.

Methods

A total of 30 healthy volunteers with 30 affected knees were involved in this cohort study (mean age, 22.0 ± 1.1 years; men, n = 14). The participants were divided into flat-walking, uphill/downhill-walking, and uphill/downhill-jogging groups and their numbers of steps taken were recorded during the effort. Moreover, medial and lateral meniscal extrusions during walking were evaluated using ultrasound three times, before and after efforts (T1) and (T2), and one day after efforts (T3), respectively.

Results

In the flat-walking group, no significant differences were observed between the follow-up periods. Conversely, in the uphill/downhill-walking and jogging groups, the medial meniscus extrusion at T2 was significantly higher than that at T1. Conversely, the medial meniscus extrusion at T3 was significantly lower than that at T2. By contrast, the lateral meniscus did not show any difference between the follow-up periods in any group.

Conclusion

Temporary extrusion of the meniscus occurred after uphill/downhill tasks in healthy volunteers, and its reaction was observed only in the medial meniscus.

Medial meniscal lesions increase antero-posterior laxity in knees with anterior cruciate ligament injury

PURPOSE

The aim of this study was to quantify the impact of concomitant meniscal lesions on knee laxity using a triaxial accelerometer in a large population of patients affected by anterior cruciate ligament (ACL) injury.

METHODS

A total of 326 consecutive patients (261 men and 65 women, mean age 31.3 ± 11.3) undergoing primary ACL reconstruction, were preoperatively evaluated through Lachman and pivot shift tests using a triaxial accelerometer to quantify knee laxity. An analysis based on the presence of meniscal tears assessed during surgery was performed to evaluate the impact of meniscal lesions on knee laxity.

RESULTS

The anterior tibial translation (Lachman test) presented significantly higher values in patients with medial meniscal lesions (7.3 ± 1.7 mm, p = 0.049) and both medial and lateral meniscal lesions (7.7 ± 1.6 mm, p = 0.001) compared to patients without concomitant meniscal lesions (6.7 ± 1.3 mm). Moreover, patients with both medial and lateral meniscal lesions presented significantly higher values of anterior tibial translation compared to patients with lateral meniscal lesions (p = 0.049). No statistically significant differences were found between the groups in terms of tibial acceleration (pivot shift test).

CONCLUSION

This study demonstrated that the contribution of concomitant meniscal lesions to knee laxity can be objectively quantified using a triaxial accelerometer in ACL-injured knees. In particular, medial meniscus lesions, alone or in association with lateral meniscus lesions, determine a significant increase of the anterior tibial translation compared to knees without meniscus tears.

LEVEL OF EVIDENCE

Level IV.

Augmentation of a Nonanatomical Repair of a Medial Meniscus Posterior Root Tear With Centralization Using Three Knotless Anchors May Be Associated With Less Meniscal Extrusion and Better Compressive Load Distribution in Mid-Flexion Compared With Non-Anatomical Root Repair Alone in a Porcine Knee Model

PURPOSE

To investigate the biomechanics of the centralization augmentation using knotless soft anchors to a nonanatomical transtibial pull-out root repair in a porcine medial meniscus posterior root tear (MMPRT) model.

METHODS

Porcine knee joints (N = 10) were used to perform one of the following procedures: (1) intact; (2) MMPRT; (3) nonanatomical root repair; (4) nonanatomical root repair with centralization using 2 anchors: anchors were inserted at the posterior medial collateral ligament (MCL) border and 10 mm anterior to the posterior MCL border; and (5) nonanatomical root repair with centralization using 3 anchors: another anchor was placed 10 mm posterior to the posterior MCL border. Contact area on the medial meniscus (MM), contact pressure in the MM and tibial cartilage, and MM extrusion were evaluated at 30°, 45°, 60°, and 90° knee flexions under 200 N compressive force.

RESULTS

MM extrusion at the posterior MCL border was significantly reduced after root repair with centralization using 3 anchors than after root repair alone at 30° (-0.063 mm vs 1.5 mm, P = .017), 45° (0.21 mm vs 1.7 mm, P = .018), and 60° (0.78 mm vs 2.3 mm, P = .019). There were no significant differences in MM extrusion between the root repair alone and root repair with centralization using 2 anchors at all flexion angles. The contact area in the middle and posterior MM was significantly greater after centralization with 3 anchors than after root repair alone at all flexion angles (except the posterior MM at 90°). The mean contact pressure in the tibial cartilage was significantly lower after centralization with 3 anchors than after root repair at all angles.

CONCLUSIONS

Augmentation of a nonanatomical repair of a medial meniscus posterior root tear with centralization using three knotless anchors may be associated with less meniscal extrusion and better compressive load distribution between 30° and 60° flexion compared with nonanatomical root repair alone in a porcine model.

CLINICAL RELEVANCE

This biomechanical study at time zero suggests that the addition of centralization using 3 knotless anchors may reduce MM extrusion and restore the load-distributing function of the MM.

Evaluation of meniscus extrusion during stair ambulation in healthy volunteers using dynamic ultrasonography: a feasibility study

PURPOSE

This study aimed to investigate the feasibility of evaluating medial meniscus extrusion (MME) during stair ambulation.

METHODS

Twenty healthy young participants (mean age, 22.4 ± 0.9 years) were recruited for this cross-sectional study. Synchronization between the three-dimensional motion system and ultrasonography was used to quantify the extent of meniscal extrusion and knee angles during different tasks, including gait, stair ascent, and stair descent. In particular, ultrasonography was used to record the movements of both the middle and posterior segments of the meniscus to obtain detailed information about these movements in relation to the knee angle. The difference between the maximum MME and the MME at the initial contact (ΔMME) was evaluated during each task in the stance phase.

RESULTS

Visualization of the meniscus in the middle segment was limited with increasing knee flexion angle, whereas the posterior segments were visible during all tasks. ΔMME of the posterior segment during stair ascent and descent was higher than that during gait (gait: 0.68 ± 0.20 mm, ascent: 1.00 ± 0.39 mm, descent: 0.90 ± 0.27 mm, gait-ascent: p = 0.009, gait-descent: p = 0.004).

CONCLUSIONS

Evaluation that includes the posterior segment enables visualization of the medial meniscus and detection of its specific behavior during stair ambulation. These findings demonstrate the feasibility of evaluating meniscus dynamics during stair ambulation, and could contribute to a better understanding of these dynamics.

Epidemiological features of acute medial meniscus posterior root tears

PURPOSE

Untreated or overlooked medial meniscus posterior root tears (MMPRTs) induce sequential knee joint degradation. We evaluated epidemiological features of acute MMPRT for its early detection and accurate diagnosis.

METHODS

Among 330 MMPRT patients from 2018 to 2020, those who underwent arthroscopic pullout repairs were enrolled. Patients who underwent non-operative treatment or knee arthroplasty, those with a cruciate ligament-deficient knee or advanced osteoarthritis of the knee, and those with insufficient data were excluded. Finally, we retrospectively evaluated data from 234 MMPRTs (female: 79.9%, complete tears: 92.7%, mean age: 65 years). Welch's t-test and Chi-squared test were used for pairwise comparisons. Spearman's rank correlation analysis was performed between age at surgery and body mass index (BMI). Multivariable logistic regression analysis with stepwise backward elimination was applied to the values as risk factors for painful popping events.

RESULTS

In both sexes, there were significant differences in height, weight, and BMI. In all patients, there was a significant negative correlation between BMI and age (ρ =  - 0.36, p < 0.001). The BMI cutoff value of 27.7 kg/m2 had a 79.2% sensitivity and a 76.9% specificity for detecting MMPRT patients aged < 50 years. A painful popping event was confirmed in 187 knees (79.9%), and the frequency was significantly reduced in partial tears as compared to complete tears (odds ratio: 0.080, p < 0.001).

CONCLUSION

Higher BMI was associated with a significantly younger age of MMPRT onset. Partial MMPRTs had a low frequency of painful popping events (43.8%).

Meniscal allograft transplantation, anterior cruciate ligament reconstruction, and valgus high tibial osteotomy for meniscal-deficient, unstable, and varus knees: surgical technique and clinical outcomes

PURPOSE

The aim of this study was to determine the clinical and functional outcome of a salvage surgical approach with the combined procedures meniscal allograft transplantation (MAT), anterior cruciate ligament reconstruction (ACLR), and high tibial osteotomy (HTO), in a cohort of patients treated for complex knee lesions evaluated up to a mid-term follow-up.

METHODS

Eight patients (38.8 ± 4.6 years, 88% males) were treated arthroscopically with MAT without bone plugs combined with primary or revision ACLR and HTO and evaluated at basal, at a minimum of two years (short follow-up), and at a mean follow-up of 5.1 years (mid-term follow-up) with the VAS score for pain, Lysholm score, IKDC subjective score, WOMAC Osteoarthritis index, and Tegner score. Physical examination (Lachman and pivot-shift tests, arthrometer assessment) and radiographic evaluation (pre- and post-operative x-rays) were obtained. Complications and failures were also recorded.

RESULTS

A statistically significant improvement was observed from baseline to five years in all clinical scores. In particular, the IKDC subjective score improved from 33.3 ± 20.7 to 73.1 ± 18.4 at short follow-up (p < 0.05), up to 78.3 ± 9.8 at the final follow-up (p < 0.05). A similar trend was demonstrated with the Lysholm, VAS, WOMAC, and Tegner score, even though only one patient reached the pre-injury activity level. Two patients had a worsening of the Kellgren-Lawrence (KL) grade from preoperative (grade 1) to final follow-up (grade 2). No major complications and surgical failures were documented.

CONCLUSION

The combined procedure of MAT, ACLR, and HTO presents few complications and failures and showed to be a valid option to reduce pain, recover knee function, and slow down the osteoarthritis process even in complex patients, with good and stable results up to a mid-term follow-up.

Biomechanical Analysis of Meniscotibial Ligament Tenodesis to Treat Meniscal Extrusion in the Setting of Posterior Medial Meniscus Root Repair

BACKGROUND

Meniscal extrusion often persists after a medial meniscus root repair. If the meniscus is extruded, the function of the meniscus as a load-sharing device and secondary knee stabilizer is compromised.

HYPOTHESIS

It was hypothesized that repairing the meniscotibial ligament (MTL) would decrease meniscal extrusion in the settings of both an isolated MTL tear and a repaired medial meniscus root while also improving medial compartment contact mechanics.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen cadaveric knees (mean age, 50.5 years) were tested in 5 conditions: intact, MTL deficiency, MTL deficiency + posterior medial meniscus root deficiency, MTL deficiency + posterior medial meniscus root repair, and MTL tenodesis + posterior medial meniscus root repair. Specimens were mounted to a load frame that applied a 1000-N axial load. Joint contact pressures were measured using thin pressure sensors, and the peak and mean pressures were analyzed. Ultrasound was used to measure meniscal extrusion.

RESULTS

The MTL tear in isolation resulted in significant meniscal extrusion compared with the intact state (P = 0.035) without a detectable difference in medial compartment pressures. The addition of a root tear to the MTL tear state resulted in significantly more extrusion (P = 0.001) and significant increases in medial compartment pressure (P = .030) compared to the MTL tear state. Root repair alone restored extrusion, mean contact pressure, and peak contact pressure back to the intact state (P > .05).

CONCLUSION

This study showed that MTL disruption led to increased meniscal extrusion in a cadaveric model. Unlike the root tear state, MTL disruption did not change contact mechanics. Furthermore, root repair alone was sufficient in restoring intact biomechanics and extrusion.

CLINICAL RELEVANCE

This study may help clinicians understand the origin of medial meniscus root tears and aid in the decision-making process for whether to add an MTL tenodesis in the setting of root repair.

Biomechanical Comparison of Two Different Sutures for the Tensile Strength of the Pullout Repair of Posterior Meniscal Root Tear

Background Medial meniscal posterior root tear has garnered attention because it causes increased joint contact pressure and loss of load distribution function. Currently, the common treatment for posterior meniscal root tears is transtibial pullout repair, and loop suture remains the gold standard procedure. Purpose The aim of this study is to validate whether the meniscus-suture complex exhibits better structural properties after loop stitch using a suture tape versus the conventional thread. Study design and methods This is a controlled laboratory study. In total, 20 menisci harvested from castrated male pigs were prepared and randomly assigned to two suturing techniques: loop stitch using ULTRATAPE (n = 10, tape group) or loop stitch using 2-0 UltraBraid (n = 10, control group). The single-loop stitch meniscus-suture technique was used. A single suture using ULTRATAPE or 2-0 UltraBraid was placed through the meniscus 5 mm medial from the resected edge of the posterior meniscus horn. The meniscus-suture complex specimens were mounted on a tensile tester to apply tensile load on the meniscus-suture complex parallel to the long axis of the stitched suture materials. Each specimen was stretched to failure at a crosshead speed of 50 mm/minute. The structural properties of the meniscus-suture complex (maximum load, linear stiffness, and elongation at failure) were determined. Results In the tape group, all the repaired complexes were torn at the ligature; conversely, in the control group, the threads were torn in three of 10 specimens, and the repaired complexes in the remaining seven specimens were torn at the ligature. No significant between-group differences were observed in linear stiffness (9.0 ± 4.1 vs 7.1 ± 2.9 N/mm) and elongation at failure (15.8 ± 6.1 vs 19.6 ± 20.1 mm); however, the tape group exhibited a significantly higher average maximum load than the control group (104.6 ± 41.2 vs 62.6 ± 32.1 N; P = 0.020). Conclusion Suture tape can be a potential alternative to the conventional thread for Medial meniscal posterior root tear repair. Clinical relevance Medial meniscal posterior root tear repair using tape rather than the conventional thread may be beneficial in obtaining better structural properties.

Medial Meniscus Posterior Root Tear: How Far Have We Come and What Remains?

Medial meniscus posterior root tears (MMRTs), defined as tears or avulsions that occur within 1 cm of the tibial attachment of the medial meniscus posterior root, lead to biomechanically detrimental knee conditions by creating a functionally meniscal-deficient status. Given their biomechanical significance, MMRTs have recently been gaining increasing interest. Accordingly, numerous studies have been conducted on the anatomy, biomechanics, clinical features, diagnosis, and treatment of MMRTs, and extensive knowledge has been accumulated. Although a consensus has not yet been reached on several issues, such as surgical indications, surgical techniques, and rehabilitation protocols, this article aimed to comprehensively review the current knowledge on MMRTs and to introduce the author's treatment strategies.

Tensile energy dissipation and mechanical properties of the knee meniscus: relationship with fiber orientation, tissue layer, and water content

Introduction: The knee meniscus distributes and dampens mechanical loads. It is composed of water (∼70%) and a porous fibrous matrix (∼30%) with a central core that is reinforced by circumferential collagen fibers enclosed by mesh-like superficial tibial and femoral layers. Daily loading activities produce mechanical tensile loads which are transferred through and dissipated by the meniscus. Therefore, the objective of this study was to measure how tensile mechanical properties and extent of energy dissipation vary by tension direction, meniscal layer, and water content. Methods: The central regions of porcine meniscal pairs (n = 8) were cut into tensile samples (4.7 mm length, 2.1 mm width, and 0.356 mm thickness) from core, femoral and tibial components. Core samples were prepared parallel (circumferential) and perpendicular (radial) to the fibers. Tensile testing consisted of frequency sweeps (0.01-1Hz) followed by quasi-static loading to failure. Dynamic testing yielded energy dissipation (ED), complex modulus (E*), and phase shift (δ) while quasi-static tests yielded Young's Modulus (E), ultimate tensile strength (UTS), and strain at UTS (ε_UTS). To investigate how ED is influenced by the specific mechanical parameters, linear regressions were performed. Correlations between sample water content (φ_w) and mechanical properties were investigated. A total of 64 samples were evaluated. Results: Dynamic tests showed that increasing loading frequency significantly reduced ED (p < 0.05). Circumferential samples had higher ED, E*, E, and UTS than radial ones (p < 0.001). Stiffness was highly correlated with ED (R² > 0.75, p < 0.01). No differences were found between superficial and circumferential core layers. ED, E*, E, and UTS trended negatively with φ_w (p < 0.05). Discussion: Energy dissipation, stiffness, and strength are highly dependent on loading direction. A significant amount of energy dissipation may be associated with time-dependent reorganization of matrix fibers. This is the first study to analyze the tensile dynamic properties and energy dissipation of the meniscus surface layers. Results provide new insights on the mechanics and function of meniscal tissue.

Meniscal Extrusion: Diagnosis, Etiology, and Treatment Options

PURPOSE OF REVIEW

The concept of meniscal extrusion has recently been recognized as a hallmark of meniscus dysfunction. This review examines contemporary literature regarding the pathophysiology, classification, diagnosis, treatment, and future directions for investigation regarding meniscus extrusion.

RECENT FINDINGS

Meniscus extrusion, defined as >3 mm of radial displacement of the meniscus, leads to altered knee biomechanics and accelerated knee joint degeneration. Meniscus extrusion has been associated with degenerative joint disease, posterior root and radial meniscal tears, and acute trauma. Meniscus centralization and meniscotibial ligament repair have been proposed as techniques to address meniscal extrusion with promising biomechanical, animal model, and early clinical reports. Further studies on the epidemiology of meniscus extrusion and associated long-term nonoperative outcomes will help to elucidate its role in meniscus dysfunction and resultant arthritic development. Understanding and appreciation for the anatomic attachments of the meniscus will help to inform future repair techniques. Long-term reporting on the clinical outcomes of meniscus centralization techniques will yield insights into the clinical significance of meniscus extrusion correction.

Biomechanical assessment of a novel meniscal scaffold compared to partial meniscectomy: A study on porcine meniscal injury

This study aimed to investigate the appropriate size of scaffold implantation on stress distribution and evaluate its mechanical and biomechanical properties considering hydrolysis. The meniscus acts as a load distribution in the knee, and its biomechanical properties are essential for the development of the PGA scaffold. We established a novel meniscal scaffold, which consists of polyglycolic acid (PGA) covered with L-lactide-ε-caprolactone copolymer (P[LA/CL]). After 4 weeks of hydrolysis, the scaffold had a 7% volume reduction compared to the initial volume. In biomechanical tests, the implantation of scaffolds 20% larger than the circumferential and vertical defect size results in greater contact stress than the intact meniscus. In the mechanical evaluation associated with the decomposition behavior, the strength decreased after 4 weeks of hydrolysis. Meanwhile, in the biomechanical test considering hydrolysis, contact stress and area equivalent to intact were obtained after 4 weeks of hydrolysis. In conclusion, the implantation of the PGA scaffold might be a useful alternative to partial meniscectomy in terms of mechanical properties, and the PGA scaffold should be implanted up to 20% of the defect size.

The Interplay of Biomechanical and Biological Changes Following Meniscus Injury

PURPOSE OF REVIEW

Meniscus injury often leads to joint degeneration and post-traumatic osteoarthritis (PTOA) development. Therefore, the purpose of this review is to outline the current understanding of biomechanical and biological repercussions following meniscus injury and how these changes impact meniscus repair and PTOA development. Moreover, we identify key gaps in knowledge that must be further investigated to improve meniscus healing and prevent PTOA.

RECENT FINDINGS

Following meniscus injury, both biomechanical and biological alterations frequently occur in multiple tissues in the joint. Biomechanically, meniscus tears compromise the ability of the meniscus to transfer load in the joint, making the cartilage more vulnerable to increased strain. Biologically, the post-injury environment is often characterized by an increase in pro-inflammatory cytokines, catabolic enzymes, and immune cells. These multi-faceted changes have a significant interplay and result in an environment that opposes tissue repair and contributes to PTOA development. Additionally, degenerative changes associated with OA may cause a feedback cycle, negatively impacting the healing capacity of the meniscus. Strides have been made towards understanding post-injury biological and biomechanical changes in the joint, their interplay, and how they affect healing and PTOA development. However, in order to improve clinical treatments to promote meniscus healing and prevent PTOA development, there is an urgent need to understand the physiologic changes in the joint following injury. In particular, work is needed on the in vivo characterization of the temporal biomechanical and biological changes that occur in patients following meniscus injury and how these changes contribute to PTOA development.

Preparation of hybrid meniscal constructs using hydrogels and acellular matrices

To search for a suitable meniscus repair material, acellular hybrid scaffolds consisting of in situ cross-linkable 3-D interpenetrating network structures were obtained by decellularization of the meniscus tissues followed by integration of the gel system. Decellularization efficiency was confirmed using a DNA quantification assay (82% decrease in DNA content) and histological stainings. In the second part of the study, the gelatin molecule was functionalized by adding methacrylic anhydride and the degree of functionalization was found to be 75% by (Proton-Nuclear Magnetic Resonance) ¹H-NMR. Using this, a series of hybrid constructs named GelMA-Hybrid (G-Hybrid), GELMA/PEGDMA-Hybrid (PG-Hybrid), and GelMA/PEGDMA/HAMA-Hybrid (PGH-Hybrid) were prepared by cross-linking with UVA. Changes in the chemical structure were determined with Fourier Transform Infrared Spectrophotometer (FTIR). Water uptake capacities of cross-linked hybrid structures were measured in swelling studies, and it was found that hybrid scaffolds showed similar swelling properties compared to native counterparts. By compressive mechanical tests, enhanced mechanical properties were revealed in cross-linked scaffolds with PGH-Hybrid having the highest cross-link density. Protein denaturation and decomposition transition temperatures were improved by adding hydrogels to acellular scaffolds according to thermal gravimetric analyses (TGA). Cross-linked acellular scaffolds have exhibited a behavior close to native tissues with below 25% mass loss in phosphate buffer saline (PBS) and enzymatic solution. Cell viability was examined through Alamar Blue on the first day and cell viability in hybrid constructs was found to be above 80% while it was closer to the control group on the 7^th day. It was concluded that the developed biomaterials could be used in meniscus tissue engineering with their tunable physicochemical and mechanical properties.

Biomechanical effects of medial meniscus radial tears on the knee joint during gait: A concurrent finite element musculoskeletal framework investigation

The biomechanical variation in the knee during walking that accompanies medial meniscal radial tears stemming from knee osteoarthritis (OA) has not been explored. This study introduced a finite element musculoskeletal model using concurrent lower limb musculoskeletal dynamics and knee joint finite element analysis in a single framework and expanded the models to include knees with medial meniscal radial tears and total medial meniscectomy. The radial tears involved three locations: anterior horn, midbody, and posterior horn with grades of 33%, 50%, and 83% of the meniscus width. The shear and hoop stresses of the tear meniscus and tibial cartilage contact load, accompanying tears, and postmeniscectomy were evaluated during the stance phase of the gait cycle using the models. In the 83% width midbody tear group, shear stress at the end of the tear was significantly greater than in the intact meniscus and other tear groups, and the maximum shear stress was increased by 310% compared to the intact meniscus. A medial meniscus radial tear has a much smaller effect on the tibial cartilage load (even though in the 83% width tear, the cartilage/total load ratio increased by only 9%). However, the contact force on the tibial cartilage with total postmeniscectomy was increased by 178.93% compared with a healthy intact meniscus, and the peak contact pressure after meniscectomy increased from 11.94 to 12.45 MPa to 17.64 and 13.76 MPa, at the maximum weight acceptance and push-off, respectively. Our study shows that radial tears with larger medial meniscus widths are prone to high stress concentrations at the end of the tears, leading to the potential risk of complete meniscal rupture. Furthermore, although the tears did not change the cartilage load distribution, they disrupted the circumferential stress-transmitting function of the meniscus, thus greatly increasing the likelihood of the onset of knee OA. The significant increase in the tibial cartilage load with total postmeniscectomy indicates a potential risk of OA flare-ups. This study contributes to a better understanding of meniscal tear-induced OA biomechanical changes during human activities and offers some potential directions for surgical guidance of meniscectomies and the prophylaxis and treatment of OA.

Transtibial Repair of Lateral Meniscus Posterior Root Tears Improves Contact Biomechanics in Pediatric Cadavers

Purpose

A paucity of data exists on the treatment of pediatric lateral meniscus root tears (LMPRTs). This study aims to characterize the biomechanics of the lateral knee joint in pediatric cadavers following LMPRT and root repair. Our hypotheses were: (1) compared with the intact state, LMPRT would be associated with decreased contact area; (2) compared with the intact state, LMPRT would be associated with increased contact pressures; and (3) compared with LMPRT, root repair would restore contact area and pressures toward intact meniscus values.

Methods

Eight cadaver knees (ages 8-12 years) underwent contact area and pressure testing of the lateral compartment. Tekscan pressure mapping sensors covering the tibial plateau were inserted underneath the lateral meniscus. Appropriate pressure load equivalents were applied by a robot at degrees of flexion: 0, 30, 60. Three meniscus conditions were tested: (1) intact, (2) complete root tear, and (3) repaired root tear. Root repairs were performed with transtibial pullout sutures. Statistical analysis was performed.

Results

Root tear significantly decreased mean contact area at 30° (P = .0279) and 60° (P = .0397). Root repair increased mean contact area and did not significantly differ from intact states. Differences in contact pressures between meniscus states were not statistically significant. Relative to the intact state. the greatest increase in contact pressures occurred between 0° and 30°. Root repair decreased mean contact pressures at 0° and 30°. At 60°, mean contact pressures of the repair state were closer in magnitude to the tear state than the intact state. Conclusions: LMPRT decreases contact area and increases contact pressures in the lateral knee compartment. Repair of LMPRT improves tibiofemoral contact area at high (>30°) degrees of flexion and contact pressures at low (<30°) degrees of flexion.

Clinical Relevance

Transosseous pullout repair is a clinically validated treatment for LMPRT. This study provides baseline biomechanics data of transtibial pullout repair of pediatric LMPRTs.

Knee adduction moment is correlated with the increase in medial meniscus extrusion by dynamic ultrasound in knee osteoarthritis

BACKGROUND

An increase in medial meniscus extrusion (MME) due to abnormal biomechanical stress leads to knee osteoarthritis (OA) progression. MME evaluation during walking is a key method of detecting dynamic changes in the meniscus, and in combination with motion analysis, can provide a deeper understanding of the mechanisms involved in the increase of MME.

OBJECTIVE

To validate the feasibility of MME dynamic evaluation in combination with a motion analysis system based on the correlation between the increase in MME and biomechanical factors.

METHODS

Twenty-three knees from 23 patients with mild to moderate knee OA were analysed in this study. The medial meniscus during walking was evaluated by ultrasound. The increase in MME was calculated as the difference between the minimum and maximum MME during walking. A three-dimensional motion analysis system was synchronised with the ultrasound and then, biomechanical factors such as knee moment and ground reaction force were evaluated.

RESULTS

The wave patterns of the mediolateral and vertical components of ground reaction forces and knee adduction moment were similar to those in the MME based on a high cross-correlation coefficient (>0.8). The increase in MME was significantly correlated with the peak value of the knee adduction moment (r = 0.54, P = 0.0073) but not with the mediolateral and vertical components of the ground reaction force.

CONCLUSION

The findings show that knee adduction moment is correlated with an increase in MME during walking and indicates the validity and feasibility of the dynamic evaluation of MME in combination with a motion analysis system.

An anatomically shaped medial meniscus prosthesis is able to partially restore the contact mechanics of the meniscectomized knee joint

Purpose

The aim of this study was to determine whether a flexible medial meniscus prosthesis is more capable of sharing loads with the direct tibiofemoral cartilage contact than the stiffer first-generation prosthesis. Additionally, the effect of the prosthesis on the tibial pressure distribution after total meniscectomy was investigated.

Methods

In an artificial knee joint, the relative amounts of load transferred through both meniscus prostheses and the direct tibiofemoral contact were assessed with pressure-sensitive sensors.

Additionally, six cadaveric knee joints were loaded in a physiological environment. Tibial contact pressures were measured with an intact native meniscus, after total meniscectomy and after implantation of the second-generation meniscus prosthesis.

Results

Whereas the first generation of the meniscus prosthesis transferred virtually all the load from femur to tibia, the second-generation prosthesis allowed for load sharing with the direct tibiofemoral contact.

No differences in load sharing were found between the native meniscus and the second-generation meniscus prosthesis. The prosthesis decreased peak and mean pressures on the medial tibial cartilage compared to meniscectomy. No significant differences in pressure were found between the native meniscus and the meniscus prosthesis.

Conclusions

The second-generation meniscus prosthesis presented in this study can share loads with the direct tibiofemoral contact, a characteristic that the first-generation prosthesis did not have.

The flexible meniscus prosthesis significantly reduces the contact pressures on the medial tibial plateau after total meniscectomy. Although the biomechanical performance of the native meniscus could not be reproduced completely, the meniscus prosthesis may have the potential to relieve post-meniscectomy pain symptoms.

In vitro method to quantify and visualize mechanical wear in human meniscus subjected to joint loading

The mechanical wear and tear of soft connective tissue from repetitive joint loading is a primary factor in degenerative joint disease, and therefore methods are needed to accurately characterize wear in joint structures. Here, we evaluate the accuracy of using a structured light 3D optical scanning system and modeling software to quantify and visualize volume loss in whole human meniscus subjected to in vitro joint loading. Using 3D printed meniscus replicas with known wear volumes, we determined that this novel imaging method has a mean accuracy of approximately 13 mm3, corresponding to a mean error of less than 7% when measuring meniscal volumetric changes of 0.2 cm3 (size of a pea). The imaging method was then applied to measure the in vitro wear of whole human menisci at four time points when a single cadaveric knee was subjected to one million cycles of controlled joint loading. The medial and lateral menisci reached steady state volumetric reductions of 0.72 cm3 and 0.34 cm3 per million cycles, respectively. Colorimetric maps of linear wear depth revealed high wear and deformation in the posterior regions of both the medial and lateral menisci. For the first time, this study has developed a method to accurately characterize volume loss in whole meniscus subjected to in vitro joint loading. This 3D scanning method offers researchers a new investigative tool to study mechanical wear and joint degeneration in meniscus, and other soft connective tissues.

Biomechanical analysis of a centralization procedure for extruded lateral meniscus after meniscectomy in porcine knee joints

The recently developed arthroscopic centralization for lateral meniscal extrusion has obtained satisfactory short-term clinical and radiological results and improves the meniscus biomechanical properties. However, the effectiveness of treatment for meniscus extrusion after partial meniscectomy still requires elucidation. This study investigated the effect of centralization with modifications from a mechanical viewpoint. Porcine knee joints (N = 6) were set in a universal tester under the following conditions: (1) Intact; (2) Meniscectomy: Inner half of the posterior half meniscus was removed; (3) Extrusion: Posterior meniscus was dislocated laterally by transecting the posterior root and the meniscotibial ligament; (4) Centralization-1: Centralization procedure using one anchor; (5) Centralization-2: Centralization procedure using two anchors; and (6) Centralization-ad: Centralization with capsular advancement using two anchors. Load distributions and contact pressure in the meniscus and tibial cartilage were evaluated with an axial compressive force of 200 N. After meniscectomy, the tibial cartilage load increased and that of the medial margin of the posterior part of the meniscus decreased. When the meniscus was extruded, the load was concentrated only on the tibial cartilage. Centralization-1 increased the load on the meniscus, while Centralization-2 further increased the meniscus load but decreased the tibial cartilage load. Centralization-ad further decreased the load on the tibial plateau. The average contact pressure of the tibial cartilage was significantly higher in the Extrusion group than in the Intact group or the Centralization-ad group. From a biomechanical viewpoint, centralization with capsular advancement was the most effective of the tested procedures for treatment for an extruded meniscus after partial meniscectomy.

Demineralized Cortical Bone Matrix Augmented With Peripheral Blood-Derived Mesenchymal Stem Cells for Rabbit Medial Meniscal Reconstruction

Tissue engineering is a promising treatment strategy for meniscal regeneration after meniscal injury. However, existing scaffold materials and seed cells still have many disadvantages. The objective of the present study is to explore the feasibility of peripheral blood-derived mesenchymal stem cells (PBMSCs) augmented with demineralized cortical bone matrix (DCBM) pretreated with TGF-β3 as a tissue-engineered meniscus graft and the repair effect. PBMSCs were collected from rabbit peripheral blood and subjected to three-lineage differentiation and flow cytometry identification. DCBM was prepared by decalcification, decellularization, and cross-linking rabbit cortical bone. Various characteristics such as biomechanical properties, histological characteristics, microstructure and DNA content were characterized. The cytotoxicity and the effects of DCBM on the adhesion and migration of PBMSCs were evaluated separately. The meniscus-forming ability of PBMSCs/DCBM complex in vitro induced by TGF-β3 was also evaluated at the molecular and genetic levels, respectively. Eventually, the present study evaluated the repair effect and cartilage protection effect of PBMSCs/DCBM as a meniscal graft in a rabbit model of medial meniscal reconstruction in 3 and 6 months. The results showed PBMSCs positively express CD29 and CD44, negatively express CD34 and CD45, and have three-lineage differentiation ability, thus can be used as tissue engineering meniscus seed cells. After the sample procedure, the cell and DNA contents of DCBM decreased, the tensile modulus did not decrease significantly, and the DCBM had a pore structure and no obvious cytotoxicity. PBMSCs could adhere and grow on the scaffold. Under induction of TGF-β3, PBMSCs/DCBM composites expressed glycosaminoglycan (GAG), and the related gene expression also increased. The results of the in vivo experiments that the PBMSCs/DCBM group had a better repair effect than the DCBM group and the control group at both 12 and 24 weeks, and the protective effect on cartilage was also better. Therefore, the application of DCBM augmented with PBMSCs for meniscus injury treatment is a preferred option for tissue-engineered meniscus.

Biomechanical consequences of anterior root detachment of the lateral meniscus and its reinsertion

Treatment of posterior meniscal roots tears evolved after biomechanical evidence of increased pressures on the tibiofemoral cartilage produced by this lesion and the subsequent accelerated development of arthritis or osteonecrosis observed clinically. However, little is known about the consequences of the detachment of the anterior roots. This in-vitro study analyzes the biomechanical changes in the tibiofemoral joint caused by avulsion of the anterior root of the lateral meniscus. The effectiveness of surgical root re-insertion to restore the pre-injured conditions is also evaluated. Using cadaveric knees at flexion angles from 0° to 90°, results show that the lesion significantly reduces the contact area and raises the pressure on the tibiofemoral cartilage of the injured compartment at all angles. Said modifications become larger at low flexion angles, which are the most frequent positions adopted by the knee in daily and sports activities, where they result similar to total meniscectomy. In-situ repair partially restores the contact biomechanics. Consequently, careful attention should be paid to proper diagnosis and treatment of detached anterior roots since the observed altered knee contact might induce similar degenerative problems in the cartilage as with completely detached posterior roots.

Mechanisms of energy dissipation and relationship with tissue composition in human meniscus

OBJECTIVE

The human meniscus is essential in maintaining proper knee joint function. The meniscus absorbs shock, distributes loads, and stabilizes the knee joint to prevent the onset of osteoarthritis. The extent of its shock-absorbing role can be estimated by measuring the energy dissipated by the meniscus during cyclic mechanical loading.

METHODS

Samples were prepared from the central and horn regions of medial and lateral human menisci from 8 donors (both knees for total of 16 samples). Cyclic compression tests at several compression strains and frequencies yielded the energy dissipated per tissue volume. A GEE regression model was used to investigate the effects of compression, meniscal side and region, and water content on energy dissipation in order to account for repeated measures within samples.

RESULTS

Energy dissipation by the meniscus increased with compressive strain from ∼0.1 kJ/m³ (at 10% strain) to ∼10 kJ/m³ (at 20% strain) and decreased with loading frequency. Samples from the anterior region provided the largest energy dissipation when compared to central and posterior samples (P < 0.05). Water content for the 16 meniscal tissues was 77.9 (C.I. 72.0-83.8%) of the total tissue mass. A negative correlation was found between energy dissipation and water content (P < 0.05).

CONCLUSION

The extent of energy dissipated by the meniscus is inversely related to loading frequency and meniscal water content.

Kinematic Analysis of Lateral Meniscal Oblique Radial Tears in the Anterior Cruciate Ligament-Deficient Knee

BACKGROUND

Lateral meniscal oblique radial tears (LMORT) occur frequently in conjunction with anterior cruciate ligament (ACL) disruption and are anatomically distinct from meniscus root tears.

HYPOTHESIS/PURPOSE

The purpose of this study was to characterize the effects of LMORT types 3 (LMORT3) and 4 (LMORT4) lesions on joint stability and meniscal extrusion in ACL-deficient knees. Our hypothesis was that both lesions would promote significant increases in anterior translation and meniscal extrusion, with the LMORT4 lesion having a greater effect.

STUDY DESIGN

Controlled laboratory study.

METHODS

Two matched pairs of cadaveric knees (n = 4) were used to optimize the testing sequence. Additional cadaveric knees with LMORT3 (n = 8) and LMORT4 (n = 8) lesions created after ACL transection underwent robotic kinematic testing for anterior drawer and pivot-shift simulations with associated ultrasound-measured meniscal extrusion at clinically relevant knee flexion angles.

RESULTS

Optimization testing showed no differences on the effect of LMORT4 lesions for anterior translation and lateral meniscal extrusion with ACL-intact versus ACL-deficient knees. ACL deficiency and LMORT3 and LMORT4 lesions with ACL deficiency were associated with significantly greater anterior translation compared with ACL-intact state for both anterior drawer and pivot-shift testing at all flexion angles (P < .001). ACL deficiency with either LMORT3 or LMORT4 lesion was associated with significantly greater anterior translation than was ACL deficiency only (P < .005) for anterior drawer testing at 90° of flexion. Meniscal extrusion was greater with LMORT3 and LMORT4 lesions compared with ACL deficiency only (P < .05) for anterior drawer at 60° of flexion and for pivot shift at 15° of flexion. The LMORT4 lesion demonstrated increased anterior translation for anterior drawer (P = .003) at 60° of flexion (12%) as well as for pivot shift at 15° of flexion (7%) and 30° of flexion (13%) (P < .005) compared with ACL deficiency only.

CONCLUSION

In this cadaveric model, the addition of an LMORT3 or LMORT4 lesion increased anterior laxity for both the anterior drawer and the pivot shift when compared with an isolated ACL tear. Lateral meniscal extrusion was also exacerbated by these LMORT lesions.

CLINICAL RELEVANCE

LMORT lesions, distinct from meniscus root tears, occur frequently in conjunction with ACL tears. This study characterized the biomechanical consequences of LMORT3 and LMORT4 lesions on joint stability and meniscal function, highlighting the importance of diagnosing and treating LMORT lesions at the time of ACL reconstruction.

Development of a Pressure-Sensitive Conductive Rubber Sensor for Analyzing Meniscal Injury in Porcine Models

The assessment of the distribution of contact pressure on the meniscus is important in the elucidation of kinematics, etiology of joint diseases, and establishment of treatment methods. Compared with sensors widely used in recent years, pressure-sensitive conductive rubber sensors are easy to mold, flexible, durable, and resistant to shearing forces. This study is aimed at developing a rubber sensor for meniscal research and evaluating the pressure distribution after meniscal injury using porcine models. After confirming the reliability of the rubber sensor, contact pressure was obtained from the rubber sensor using the medial meniscus and femur of the porcine knee. Three test conditions of intact meniscus, radial tear, and meniscectomy were prepared, and a compressive load of 100 N was applied. After confirming the high reliability of the rubber sensor, the intact meniscus had the most uniform pressure distribution map, while the pressure in the meniscectomy model was concentrated in the resection region. The high-pressure region was significantly smaller in the intact group than in the radial tear models after 80 and 100 N (P < 0.05). The rubber sensor captured the pressure concentration specific to each examination group and was useful for evaluating the relationship between the pattern of meniscal injury and changes in the biomechanical condition of the knee.

The influence of the steep medial posterior tibial slope on medial meniscus tears in adolescent patients: a retrospective case-control study

Background

Several studies have demonstrated a relationship between the posterior tibial slope (PTS) and meniscal tears in adults. However, little is known about the association between the PTS of the adolescents and medial meniscal tears (MMT). The purpose of this study was to evaluate the association between the PTS and MMT in adolescents, and to determine the optimal cut-off values of PTS for discriminating between the MMT and the control groups.

Methods

Between January 2018 and January 2020, a retrospective case-control study was performed. In this study, isolated MMT adolescent patients with no ligamentous injuries were matched by age and sex to a control group of radiologically normal images. The PTS was defined as the angle between the perpendicular line to proximal tibial cortex (PTC) and the tangent line along the tibial plateau. Then, both the medial posterior tibial slope (MPTS) and lateral posterior tibial slope (LPTS) were measured by plain radiographs on the lateral views. In addition, the optimal cut-off values of PTS were determined by the receiver operating characteristic (ROC) curve analysis.

Results

A total of seventy-two patients who met the inclusion criteria were enrolled in the final analysis (36 patients with isolated MMT, 36 controls). The MPTS was greater in the knees with isolated MMT (10.7° ± 2.1°) than that of the control group (8.8° ± 1.7°), showing significant difference (P<0.001). However, there was no significant difference regarding the LPTS between the isolated MMT and controls (11.5 ± 3.4 vs 10.9 ± 2.6, p>0.05). In the ROC curve analysis, the calculated cutoff value of the MPTS discriminating between the groups was 10.3°, with a sensitivity of 73.3% and specificity of 78.9%.

Conclusions

This study demonstrated that steep MPTS is associated with MMT, and MPTS≥10.3° was identified to be a risk factor for MMT in adolescents.

Architecture of the cancellous bone in human proximal tibia based on P45 sectional plastinated specimens

PURPOSE

To reveal differences in the pattern of trabecular architecture in the epiphysis and metaphysis of the proximal tibia.

METHODS

The trabecular architecture of the proximal tibia was observed in 27 P45 plastinated knee specimens.

RESULTS

In the medial and lateral condyles, under the articular cartilage surrounded by the medial or lateral meniscus, the cancellous bone is formed by thick and dense trabecular bands, which run longitudinally in the epiphysis and then pass through the epiphyseal line to terminate on the slanted cortex of the metaphysis. In the intercondylar eminence, the trabeculae are arranged basically in a network. In the central portion of the tibial metaphysis, cancellous bone consists of fine arcuate trabeculae, which extend to the anterior and posterior cortices, respectively. These trabeculae are intersected sparsely and form trusses over the medullary cavity. Near the areas of attachment of the iliotibial tract, tibial collateral ligament, anterior and posterior cruciate ligaments, and patellar ligament, the cancellous bone is locally reinforced with patchy trabeculae, dense radiating trabeculae, or two orthotropic trabecular bands.

CONCLUSION

This study provides further accurate anatomical information on the trabeculae of the proximal tibia. The soft structures of knee joint, including the articular cartilage, menisci, and ligaments, and the slanted cortices of the metaphysis are important landmarks for the location of different arrangements of the cancellous architecture. The present results are beneficial for clinical diagnosis and treatment of pathologies of the knee joint, or the establishment of a finite element analysis model of the knee joint.

Anterior Cruciate Ligament Reconstruction With Concomitant Meniscal Repair: Is Graft Choice Predictive of Meniscal Repair Success?

Background

When meniscal repair is performed during anterior cruciate ligament (ACL) reconstruction (ACLR), the effect of ACL graft type on meniscal repair outcomes is unclear.

Hypothesis

The authors hypothesized that meniscal repairs would fail at the lowest rate when concomitant ACLR was performed with bone--patellar tendon--bone (BTB) autograft.

Study Design

Cohort study; Level of evidence, 3.

Methods

Patients who underwent meniscal repair at primary ACLR were identified from a longitudinal, prospective cohort. Meniscal repair failures, defined as any subsequent surgical procedure addressing the meniscus, were identified. A logistic regression model was built to assess the association of graft type, patient-specific factors, baseline Marx activity rating score, and meniscal repair location (medial or lateral) with repair failure at 6-year follow-up.

Results

A total of 646 patients were included. Grafts used included BTB autograft (55.7%), soft tissue autograft (33.9%), and various allografts (10.4%). We identified 101 patients (15.6%) with a documented meniscal repair failure. Failure occurred in 74 of 420 (17.6%) isolated medial meniscal repairs, 15 of 187 (8%) isolated lateral meniscal repairs, and 12 of 39 (30.7%) of combined medial and lateral meniscal repairs. Meniscal repair failure occurred in 13.9% of patients with BTB autografts, 17.4% of patients with soft tissue autografts, and 19.4% of patients with allografts. The odds of failure within 6 years of index surgery were increased more than 2-fold with allograft versus BTB autograft (odds ratio = 2.34 [95% confidence interval, 1.12-4.92]; P = .02). There was a trend toward increased meniscal repair failures with soft tissue versus BTB autografts (odds ratio = 1.41 [95% confidence interval, 0.87-2.30]; P = .17). The odds of failure were 68% higher with medial versus lateral repairs (P < .001). There was a significant relationship between baseline Marx activity level and the risk of subsequent meniscal repair failure; patients with either very low (0-1 points) or very high (15-16 points) baseline activity levels were at the highest risk (P = .004).

Conclusion

Meniscal repair location (medial vs lateral) and baseline activity level were the main drivers of meniscal repair outcomes. Graft type was ranked third, demonstrating that meniscal repairs performed with allograft were 2.3 times more likely to fail compared with BTB autograft. There was no significant difference in failure rates between BTB versus soft tissue autografts.

Registration

NCT00463099 (ClinicalTrials.gov identifier).

The association of meniscal body height with knee structural changes in middle-aged and elderly patients with symptomatic knee osteoarthritis

OBJECTIVES

To investigate whether and how meniscal height is associated with osteoarthritis (OA)-related knee structural changes in symptomatic knee OA.

METHODS

We studied 106 patients (61 female, aged 40-73 years) with symptomatic knee OA. X-ray was used for Kellgren-Lawrence score. Meniscal body heights and extrusion were measured on coronal sections of intermediate-weighted MRI sequence. Knee structural changes were assessed using the modified whole-organ magnetic resonance imaging score (WORMS). Associations between meniscal body height and knee structural changes were assessed using linear regression analysis.

RESULTS

Higher medial meniscal body height was significantly associated with severe medial meniscal lesions (p = 0.001-0.023), medial compartmental cartilage lesions (p = 0.045), patellofemoral compartmental and medial compartmental bone marrow edema patterns (p = 0.001-0.037), anterior cruciate ligament and patellar ligament abnormalities (p = 0.020-0.023), and loose bodies (p = 0.017). However, lateral meniscal body height was negatively correlated with WORMS scores for lateral meniscal lesions (p ≤ 0.018), lateral compartmental cartilage lesions (p ≤ 0.011), and lateral compartmental bone marrow edema patterns (p = 0.038).

CONCLUSION

Higher medial meniscal body height was associated with more severe medial compartment structural abnormalities and patellofemoral bone marrow edema patterns, while lateral meniscal body height was inversely correlated with the severity of lateral compartment structural abnormalities.

ADVANCES IN KNOWLEDGE

Our study revealed that meniscal body height was associated with multiple OA-related knee structural changes, which would be beneficial in identifying patients with or at risks for knee OA.

Placement of an anatomic tibial tunnel significantly improves the medial meniscus posterior extrusion at 90° of knee flexion following medial meniscus posterior root pullout repair

PURPOSE

The purpose of this study was to evaluate the influence of tibial tunnel position in pullout repair for a medial meniscus (MM) posterior root tear (MMPRT) on postoperative MM extrusion.

METHODS

Thirty patients (median age 63 years, range 35-72 years) who underwent transtibial pullout repairs for MMPRTs were included. Three-dimensional computed tomography images of the tibial surface were evaluated using a rectangular measurement grid for assessment of tibial tunnel position and MM posterior root attachment. Preoperative and postoperative MM medial extrusion (MMME) and posterior extrusion (MMPE) at 10° and 90° knee flexion were measured using open magnetic resonance imaging.

RESULTS

Tibial tunnel centers were located more anteriorly and more medially than the anatomic center (median distance 5.8 mm, range 0-9.3 mm). The postoperative MMPE at 90° knee flexion was significantly reduced after pullout repair, although there was no significant reduction in MMME or MMPE at 10° knee flexion after surgery. In the correlation analysis of the displacement between the anatomic center to the tibial tunnel center and improvements in MMME, and MMPE at 10° and 90° knee flexion, there was a significant positive correlation between percentage distance and improvement of MMPE at 90° knee flexion.

CONCLUSION

This study demonstrated that the nearer the tibial tunnel position to the anatomic attachment of the MM posterior root, the more effective the reduction in MMPE at 90° knee flexion. Our results emphasize that an anatomic tibial tunnel should be created in the MM posterior root to improve the postoperative MMPE and protect the articular cartilage in a knee flexion position. Placement of an anatomic tibial tunnel significantly improves the MMPE at 90° of knee flexion after MM posterior root pullout repair.

LEVEL OF EVIDENCE

IV.

Progress in the treatment of knee osteoarthritis with high tibial osteotomy: a systematic review

BACKGROUND

High tibial osteotomy (HTO) has been used for over 60 years in clinical practice and mainly comprises two major techniques: closed wedge high tibial osteotomy (CWHTO) and open wedge high tibial osteotomy (OWHTO). However, these have been gradually replaced by total knee arthroplasty (TKA), due to inconsistent clinical results and many complications. With the concept of knee-protection and ladder treatment of osteoarthritis, as an effective minimally invasive treatment for knee osteoarthritis, HTO has once again received attention.

METHODS

A systematic literature search was conducted in PubMed, Embase, ClinicalKey, CNKI, and the China Wanfang database. The search terms relating to osteoarthritis and high tibial osteotomy were used. Studies were considered eligible if the participants were adults with knee osteoarthritis (KOA) who had undergone HTO. A total of two reviewers participated in the selection of the studies. Reviewer 1 was assigned to screen titles and abstracts, and reviewer 2 to screen full-text data. Data extraction was completed by reviewer 2, and 30% were checked by the research team. Potential conflicts were resolved through discussion. The methodological quality was assessed using a risk of bias, based on the Cochrane handbook and Newcastle-Ottawa assessment scale. The outcome indicators are (1) posterior slope of tibial plateau, (2) the height of the patella, (3) fracture in the osteotomy plane, (4) survival rate, (5) special surgery knee score (HSS), and (6) the recurrence of varus deformity of the included studies were evaluated according to the guidelines of the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) working group (Atkins et al., BMJ 328:1490, 2004).

RESULTS

Among the 18 articles included, 10 were prospective cohort studies, five were randomized controlled trial (RCT) studies, one was prospective comparative study (PCS), one was retrospective comparative study (RCS), and one was retrospective cohort. The earliest publication year was 1999, and the most recent was 2018. A total of 6555 eligible cases were included, comprised of 3351 OWHTO patients and 3204 CWHTO patients. Five RCT were assessed using risk of bias, based on the Cochrane handbook. Eleven cohort studies and two case-control studies were assessed using the Newcastle-Ottawa assessment scale. These six outcome indicators for a total of twenty-four evidence individuals were evaluated separately, among which the GRADE classification of 1, 2, and 6 was medium quality, and 3, 4, and 5 were low quality. Based on our systematic review, regardless of whether the chosen procedure was OWHTO or CWHTO, both HSS scores increased significantly as compared with the preoperative scores. Compared with CWHTO, the height of the patella and tibial posterior slope angle increased following OWHTO. Additionally, OWHTO has a better long-term survival rate and lower fracture rate, supporting OWHTO as the first treatment choice.

CONCLUSIONS

For young patients with knee osteoarthritis (KOA), high tibial osteotomy (HTO) can be considered as a treatment option to replace total knee arthroplasty (TKA) to reduce the economic burden and promote the reasonable allocation of medical resources. This study shows that compared with CWHTO, OWHTO has certain advantages in long-term survival rate and lower fracture rate, but the level of evidence is lower. In the future, we will need larger sample sizes and longer follow-up randomized controlled trials to improve our research.

Different effects of the lateral meniscus complete radial tear on the load distribution and transmission functions depending on the tear site

PURPOSE

To compare the effect of the lateral meniscus (LM) complete radial tear at different tear sites on the load distribution and transmission functions.

METHODS

A compressive load of 300 N was applied to the intact porcine knees (n = 30) at 15°, 30°, 60°, 90°, and 120° of flexion. The LM complete radial tears were created at the middle portion (group M), the posterior portion (group P), or the posterior root (group R) (n = 10, each group), and the same loading procedure was followed. Finally, the recorded three-dimensional paths were reproduced on the LM-removed knees. The peak contact pressure (contact area) in the lateral compartment and the calculated in situ force of the LM under the principle of superposition were compared among the four groups (intact, group M, group P, and group R).

RESULTS

At all the flexion angles, the peak contact pressure (contact area) was significantly higher (lower) after creating the LM complete radial tear as compared to that in the intact state (p < 0.01). At 120° of flexion, group R represented the highest peak contact pressure (lowest contact area), followed by group P and group M (p < 0.05). The results of the in situ force carried by the LM were similar to those of the tibiofemoral contact mechanics.

CONCLUSION

The detrimental effect of the LM complete radial tear on the load distribution and transmission functions was greatest in the posterior root tear, followed by the posterior portion tear and the middle portion tear in the deep-flexed position. Complete radial tars of the meniscus, especially at the posterior root, should be repaired to restore the biomechanical function.

The correlation between osteoarthritis stage and the effect of the lateral wedge insole for 3 months on medial meniscus extrusion in the knee joint

BACKGROUND

Medial meniscus extrusion (MME) leads to symptomatic knee osteoarthritis (OA) due to increased mechanical stress. MME increases with weight-bearing, and the difference in MME between non-weight-bearing and weight-bearing status (ΔMME) is a factor that causes greater MME. The lateral wedge insole (LWI) is an ideal approach for decreasing the amount of ΔMME associated with the reduction of medial loading stress in the early stage of knee OA. However, the effect of the LWI for 3 months on the ΔMME and its response to OA stage have not been elucidated.

OBJECTIVE

To investigate the effects of the LWI for 3 months on MME and the ΔMME in each stage of OA.

METHODS

Participants were divided into three groups: no intervention with the LWI (control group; n = 9) and intervention with the LWI in early OA (early OA group: Kellgren-Lawrence (K/L) stage = 2, n = 17) and late OA (late OA group: K/L stage > 2, n = 13). MME was evaluated using ultrasound, and the ΔMME was obtained as the difference in MME from non-weight-bearing and weight-bearing conditions. These measurements were performed at two time points: the initial office visit as a baseline and post-3 months.

RESULTS

The weight-bearing MME and ΔMME values post-3 months were significantly decreased compared with those at baseline in the early OA group but not in the control or late OA groups.

CONCLUSIONS

The use of the LWI for 3 months decreased weight-bearing MME and ΔMME values, and its effectiveness was more pronounced in the early stage of knee OA.

MR imaging pattern of tibial subchondral bone structure: considerations of meniscal coverage and integrity

OBJECTIVES

To compare regional differences in subchondral trabecular structure using high-resolution MRI in meniscus-covered/meniscus-uncovered tibia in cadaveric knees with intact/torn menisci.

MATERIALS AND METHODS

3D proton density CUBE MRI of 6 cadaveric knees without significant osteoarthritis (OA) was acquired, 0.25-mm resolution. Menisci were evaluated and classified intact or torn. MR data were transferred to ImageJ program to segment tibial 3D volume of interest (VOI). Data was subdivided into meniscus-covered/meniscus-uncovered regions. Segmented VOI was classified into binary data, trabeculae/bone marrow. The trabecular bone data was used to measure MR biomarkers (apparent subchondral plate-connected bone density (adapted from spine MR), apparent trabecular bone volume fraction, apparent mean trabecular thickness, apparent connectivity density, and structure model index (SMI)). Mean value of parameters was analyzed for the effects of meniscal tear/tibial coverage.

RESULTS

Nine torn menisci and 3 intact menisci were present. MR measures of bone varied significantly due to meniscal coverage/tear. Subchondral plate-connected bone density under covered meniscus regions increased from 10.9 to 23.5% with meniscal tear. Values increased in uncovered regions, 19.3% (intact) and 32.4% (torn). This reflects higher density when uncovered (p = 0.048) with meniscal tear (p = 0.007). Similar patterns were found for trabecular bone fraction (coverage p < 0.001, tear p = 0.047), trabecular thickness (coverage p = 0.03), connectivity density (coverage p = 0.002), and SMI (coverage p = 0.015).

CONCLUSION

Quantitative trabecular bone evaluation emphasizes intrinsic structural differences between meniscus-covered/meniscus-uncovered tibias. Results offer insight into bone adaptation with meniscal tear and support the hypothesis that subchondral bone plate-connected bone density could be important in early subchondral bone adaptation.

Traumatic avulsion of the anterior medial meniscus root combined with PCL injury: a case report

Background

Avulsion of the anterior medial meniscus root (AMMR) has a low incidence rate, especially when it is combined with posterior cruciate ligament (PCL) injury, which hasn’t been reported in any literature to date. The aim of this study was to share our experience in the diagnosis and treatment of a patient with traumatic avulsion of AMMR combined with PCL injury.

Case presentation

This article reports a 26-year-old male patient diagnosed with traumatic avulsion of the AMMR with PCL injury. After arthroscopic surgery, he achieved remission of symptoms and recovery of functions.

Conclusions

Anterior meniscus root injuries are relatively rare. Its diagnosis can be made preliminarily based on clinical manifestations, physical examinations, and magnetic resonance imaging (MRI), and then confirmed by arthroscopic exploration. Arthroscopic suture anchor fixation of the injured anterior meniscus horn shows a good therapeutic effect.

Dynamic ultrasonography of the medial meniscus during walking in knee osteoarthritis

BACKGROUND

Medial meniscal extrusion (MME) is a risk factor for the progression of knee osteoarthritis (OA). MME evaluation is crucial and it is commonly performed using magnetic resonance imaging (MRI) or static ultrasonography. We developed a prototype flat-shaped ultrasound transducer to visualize the actual meniscal movements during walking.

OBJECTIVE

The aim of this study was to investigate whether it is feasible to visualize and evaluate the meniscal movements during walking using the novel flat-shaped ultrasound transducer for dynamic ultrasonography.

METHODS

Six participants who were diagnosed with primary unilateral or bilateral tibiofemoral knee OA on radiography (mean age, 67.1 ± 9.9 years; males/females, 4/2) and six healthy volunteers without any symptoms in their knees (mean age, 26.3 ± 4.0 years; males/females, 4/2) were enrolled in this study. The movement of the medial meniscus during walking was visualized using the novel transducer and the gait motion was recorded as video images that were synchronized with the ultrasonogram. MME and ΔMME (the difference between the minimum and maximum MME during the stance phase of the gait cycle) were evaluated in those with OA and compared with those in healthy volunteers.

RESULTS

In both groups, MME was visualized clearly in the stance phase. The mean values of MME and ΔMME in the knee OA group were significantly greater than those in the control group (P < .01).

CONCLUSIONS

Dynamic meniscal movement during gait can be evaluated with the specially developed novel ultrasound transducer. Our approach will be helpful in unveiling unknown pathological mechanisms in knee OA.

Increase in medial meniscal extrusion in the weight-bearing position observed on ultrasonography correlates with lateral thrust in early-stage knee osteoarthritis

BACKGROUND

Lateral thrust is known to be risk factors for knee osteoarthritis progression. Medial meniscus extrusion is also known to be risk factors for knee osteoarthritis progression; moreover, the amount of change in medial meniscus extrusion from non-weight bearing to weight bearing is an important factor for the progression of knee osteoarthritis. This study aimed to investigate the correlation between lateral thrust and the change in medial meniscus extrusion.

METHODS

In total, 44 knees from 44 patients (mean age, 68.9 years) with knee osteoarthritis were divided into two groups according to the Kellgren-Lawrence grade: early-stage osteoarthritis (Kellgren-Lawrence = 2) and severe osteoarthritis (Kellgren-Lawrence = 3 or 4). The lateral thrust during gait, represented as the lateral acceleration peak immediately after heel strike, was recorded by an inertial sensor. The amount of change in medial meniscus extrusion, which was the difference between weight-bearing (unipedal standing) and non-weight-bearing (supine) conditions, was evaluated using ultrasonography.

RESULTS

The mean value of the lateral acceleration peak in the severe osteoarthritis group was higher than that of the early-stage osteoarthritis group (p < 0.05). The non-weight-bearing and weight-bearing medial meniscus extrusion in the severe OA group were significantly higher than those of the early-stage osteoarthritis group (p < 0.001). However, the amount of change in medial meniscus extrusion in severe osteoarthritis group was significantly lower than in the early-stage osteoarthritis group (p < 0.05). The amount of change in medial meniscus extrusion showed a significant correlation with the lateral acceleration peak in the early-stage osteoarthritis group (r = 0.56, p < 0.001). On the other hand, there was no significant correlation in the severe osteoarthritis group.

CONCLUSION

The lateral thrust shows a positive correlation with the amount of change in medial meniscus extrusion by weight bearing in patients with early-stage knee osteoarthritis.

Medial Meniscal Posterior Horn Tears Are Associated With Increased Posterior Tibial Slope: A Case-Control Study

BACKGROUND

While the medial meniscal posterior horn (MMPH) is reported to bear a considerable portion of overall load on the knee joint, including compressive and shear forces, no study has yet investigated the relationship between the MMPH and posterior tibial slope (PTS), which is a geometric factor associated with the shear force component in the presence of a compressive load in the knee joint.

HYPOTHESIS/PURPOSE

The purpose was to investigate the relationship between the PTS and MMPH tears in patients without ligamentous injury. It was hypothesized that the PTS is greater in patients with MMPH tears as compared with those without.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

From March 2015 to December 2018, 159 patients with isolated MMPH tears and 60 patients without any pathologic findings on magnetic resonance imaging (control group) were included in this study. The PTS in the affected and contralateral knees was compared between the groups, which were statistically matched according to baseline characteristics (ie, age, sex, body mass index, radiographic osteoarthritis grade according to the Kellgren-Lawrence scale, and hip-knee-ankle angle) via the inverse probability of treatment weighting method. Furthermore, the MMPH tear group was subdivided according to meniscal tear patterns; these subgroups were then compared with the control group.

RESULTS

The mean PTS was significantly greater in the MMPH tear group than in the control group (affected knee: MMPH tear group, 7.0°± 3.4° [mean ± SD]; control group, 5.2°± 2.1°, P < .001; contralateral knee: MMPH tear group, 6.7°± 3.3°; control group, 4.7°± 2.2°, P < .001). The mean PTS in each subgroup also tended to be greater than that in the control group. In the receiver operating characteristic curve analysis, the cutoff point of the PTS discriminating between the MMPH tear and control groups was 6.6° for the affected knee (sensitivity, 55.3%; specificity, 75.0%) and 5.5° for the contralateral knee (sensitivity, 61.0%; specificity, 76.7%).

CONCLUSION

An increased PTS is strongly associated with an increased incidence of MMPH tears and less affected by the meniscal tear patterns.

Use of magnetic resonance imaging to determine laterality of meniscal size in healthy volunteers

Introduction

The menisci are responsible for several functions. They are shock absorbers during dynamic loading on the knee and provide a broader surface area on which to distribute stress evenly to the tibia and femur. These functions allow for smoother movement and greater stability of the knee joint. Meniscal injury can be a great impediment to the function of the knee. Therefore, in the case of meniscal injury, our main concern is the relief of patient symptoms, followed by consequent restoration of meniscal function to the greatest of our ability.

To prevent the long terms effects of a meniscectomy, meniscal allograft transplantation (MAT) was developed. The potential of using the size of the contralateral healthy menisci, to determine the size of the menisci to be replaced, will be discussed.

Methods

Knee MRIs done on healthy patients in the past 5 years were reviewed. Magnetic Resonance Imaging was performed using a 3-T scanner. Each individual was examined with knee joints in full extension. Measurements were performed two separate times, two weeks apart. A mean of three measurements was made during each session to reduce error.

Thirty-eight normal bilateral knee joints MRIs remained (16 males, 22 females). Participants were sampled from the institutional Picture Archiving and Communication System (PACS). Age, gender, and the medial meniscal and lateral meniscal size of both knees were recorded. The laterality of the menisci was compared between both knees in each patient.

Results

A total of 38 patients were included in this study, with a mean age of 37.39 (±9.50) years. They were 16 (42.1%) men and 22 (57.9%) women. We didn’t find any significant difference in the mid-coronal section between left and right knees meniscal measurements. None of the measurements were significantly different between men and women. There was no significant difference in the medial mid-sagittal section or lateral mid-sagittal section between left and right knee meniscal measurements.

Conclusion

The results obtained in this study may support the use of MRI of the bilateral knee to obtain an appropriately sized allograft.

Biomechanical analysis of the centralization procedure for extruded lateral menisci with posterior root deficiency in a porcine model

PURPOSE

The purpose of this study was to investigate the biomechanical properties of load distribution following a centralization procedure for extruded lateral menisci with posterior root deficiency in a porcine model.

METHODS

Six porcine knee joints were analyzed in a universal tester, as follows: 1) Intact; 2) Extrusion (meniscus extrusion was created by resecting the posterior root of the lateral meniscus, as well as the posterior synovial capsule); and 3) Centralization (two anchors were inserted at the lateral tibial plateau, and the meniscus was sutured to secure it close to the original position). Meniscus extrusion was evaluated using two markers put on the posterior cruciate ligament and the lateral meniscus, and the load distribution were assessed using a pressure mapping sensor system after applying a loading force of 200 N to the knee joint.

RESULTS

Distance between two markers (mm, Average; 95% CI) was larger in the extrusion group (21.9; 17.8, 25.6) than in the intact (18.1; 15.1, 22.7) or the centralization (15.3; 12.9, 18.0) groups. The contact area (mm²) in the middle of the meniscus was significantly smaller in the extrusion group (45.8; 18.5, 73.2) than in the intact (85.7; 72.1, 99.2) or the centralization (98.3; 88.8, 107.8) groups. The maximum contact pressure (MPa) in the tibial plateau was significantly higher in the extrusion group (0.37; 0.35, 0.40) than in the intact (0.29; 0.21, 0.37) or the centralization (0.29; 0.22, 0.36) groups.

CONCLUSIONS

The centralization procedure enabled a reduction of the meniscus extrusion in the lateral meniscus with posterior root deficiency and restored the maximum load and contact pressure to values close to those of the normal knee joint.

PCL-MECM-Based Hydrogel Hybrid Scaffolds and Meniscal Fibrochondrocytes Promote Whole Meniscus Regeneration in a Rabbit Meniscectomy Model

Regeneration of an injured meniscus continues to be a scientific challenge due to its poor self-healing potential. Tissue engineering provides an avenue for regenerating a severely damaged meniscus. In this study, we first investigated the superiority of five concentrations (0%, 0.5%, 1%, 2%, and 4%) of meniscus extracellular matrix (MECM)-based hydrogel in promoting cell proliferation and the matrix-forming phenotype of meniscal fibrochondrocytes (MFCs). We found that the 2% group strongly enhanced chondrogenic marker mRNA expression and cell proliferation compared to the other groups. Moreover, the 2% group showed the highest glycosaminoglycan (GAG) and collagen production by day 14. We then constructed a hybrid scaffold by 3D printing a wedge-shaped poly(ε-caprolactone) (PCL) scaffold as a backbone, followed by injection with the optimized MECM-based hydrogel (2%), which served as a cell delivery system. The hybrid scaffold (PCL-hydrogel) clearly yielded favorable biomechanical properties close to those of the native meniscus. Finally, PCL scaffold, PCL-hydrogel, and MFCs-loaded hybrid scaffold (PCL-hydrogel-MFCs) were implanted into the knee joints of New Zealand rabbits that underwent total medial meniscectomy. Six months postimplantation we found that the PCL-hydrogel-MFCs group exhibited markedly better gross appearance and cartilage protection than the PCL scaffold and PCL-hydrogel groups. Moreover, the regenerated menisci in the PCL-hydrogel-MFCs group had similar histological structures, biochemical contents, and biomechanical properties as the native menisci in the sham operation group. In conclusion, PCL-MECM-based hydrogel hybrid scaffold seeded with MFCs can successfully promote whole meniscus regeneration, and cell-loaded PCL-MECM-based hydrogel hybrid scaffold may be a promising strategy for meniscus regeneration in the future.

Effect of physical therapy on early knee osteoarthritis with medial meniscal posterior tear assessed by MRI T2 mapping and 3D-to-2D registration technique: A prospective intervention study

Objectives: The purpose of this study was to verify that exercise aimed at improving knee kinematics in early-stage knee osteoarthritis (OA) patients with medial meniscus posterior root tears (MMPRTs) reduces knee adduction angle during gait and prevents rapid cartilage degeneration in the medial compartment of the knee.Methods: Subjects were randomly assigned to an adapting alignment exercise (AAE) group, with the goal of improving knee kinematics, and a muscle training and exercise (MTE) group. Before the start of the six-month intervention and following its completion, we performed an analysis of knee kinematics during gait using a 3D-to-2D registration technique and identified the area of cartilage degeneration using MRI T2 mapping.Results: The amount of change between pre- and post-intervention measurements of the maximum angle of adduction was 0.48° (95% CI: -0.14, 1.09) in the MTE group and -0.40° (-0.84, 0.04) in the AAE group (p = .039). The amount of change in the area of cartilage degeneration according to MRI T2 mapping expressed as MTE/AAE group was 7.7 mm² (-0.4, 15.8)/-2.7 mm² (-10.8, 5.3) at the posterior knee (p = .043).Conclusion: AAE could be a potential treatment method that improves the natural course of knee OA with MMRPTs.

Anterior Cruciate Ligament Reconstruction in Young Female Athletes: Patellar Versus Hamstring Tendon Autografts

BACKGROUND

Female athletes are 2 to 8 times more prone to anterior cruciate ligament (ACL) rupture than males. Furthermore, reinjury to the ipsilateral or contralateral knee can occur in >20% of athletes. Female sex and younger age are known risk factors for graft failure. The optimal graft choice for young females remains unknown and poorly studied.

PURPOSE/HYPOTHESIS

The authors aimed to compare clinical outcomes in young females who underwent ACL reconstruction (ACLR) with bone-patellar tendon-bone (BTB) and quadrupled hamstring (HS) autografts. It was hypothesized that no significant differences in outcomes exist between graft choices.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Female patients aged 15 to 25 years who underwent primary ACLR with BTB or HS autograft were included for review. Patients were subdivided into 2 age groups: 15 to 20 years and 21 to 25 years. The occurrence of chondral, meniscal, or ligamentous injury to either knee was recorded for comparison.

RESULTS

A total of 256 females were included (BTB, n = 175; HS, n = 81). The majority of patients were between the ages of 15 and 20 years (BTB, 80%; HS, 77.8%). Overall, graft rupture occurred in 23 patients (9%) and contralateral ACL tear occurred in 18 (7%). Subgroup analysis showed that 75% of BTB and 100% of HS graft retears occurred in females aged 15 to 20 years. Within this age group, there was a significantly lower rate of graft ruptures in the BTB group (6.4%) as compared with the HS group (17.5%, P = .02). Allograft augmentation was used in 4 of the 11 HS grafts that retore. When allograft-augmented grafts were excluded, there was no significant difference in graft failure rate between graft choices. Fifteen patients in the BTB group (12%) as opposed to 1 in the HS group (2%) reported extreme difficulty or the inability to kneel on the front of the knee (P = .04).

CONCLUSION

In females aged 15 to 20 years undergoing ACLR, BTB autograft may lead to fewer graft ruptures than HS autograft. While this difference was not observed in females aged 21 to 25 years, a larger sample may be required to accept the null hypothesis in this age group. BTB autograft significantly increased the risk of kneeling pain as compared with HS regardless of age.

Dynamic intraligamentary stabilization of anterior cruciate ligament repair: hardware removal has no effect on knee laxity at 2-year follow-up

INTRODUCTION

Dynamic intraligamentary stabilization (DIS) stabilizes the knee joint during anterior cruciate ligament (ACL) healing. After 6 months, tibial hardware removal is offered to the patients if local discomfort at the implant site is present.

AIM

This study compared knee laxity and functional scores 2 years after DIS between patients with and without hardware removal. It is hypothesized that it does not affect ACL healing.

MATERIALS AND METHODS

The study retrospectively analyzed prospectively collected data from 173 patients with either hardware removal (n = 47) or no additional intervention (n = 126). Inverse probability of treatment weighting using the propensity score was applied to balance the groups for baseline characteristics. The primary outcome was the side-to-side difference in knee laxity measured with the rolimeter at manual maximum force (Δ-Lachman). Secondary outcomes were the pivot-shift test and subjective scores.

RESULTS

Mean age was 34 years in both groups, and female gender was 47% (hardware removal group) and 50% (control group), respectively. No significant differences were found for Δ-Lachman (p = 0.09), pivot-shift test (p = 0.41), and subjective scores (p > 0.10) two years after DIS.

CONCLUSION

Knee laxity 2 years after DIS in patients with tibial hardware removal and patients without hardware removal was not significantly different. The groups were also similar regarding all the assessed functional scores. This study confirms the hypothesis that the healing ACL resumes its stabilizing role, and the hardware can be removed beginning 6 months after surgery without adverse consequences for joint stability.

LEVEL OF EVIDENCE

Case-control study, Level III.