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Purpose: This study aimed to evaluate the association between the progression of medial joint space (MJS) narrowing, medial meniscus extrusion (MME) and clinical scores and the tibial tunnel position in pullout repairs for medial meniscus posterior root tears (MMPRTs). Methods: This retrospective study examined 54 patients. Changes in MJS (ΔMJS), MME (ΔMME) and clinical scores and their relationship with the tibial tunnel position were evaluated using correlation coefficients. The distance from the anatomical to technical attachment position in the tibial tunnel position was measured in the anterior and medial directions, and the direct distance was measured using the Pythagorean theorem. Results: The mean ΔMJS and ΔMME were 0.6 ± 0.8 and 1.3 ± 1.3 mm, respectively, and the mean anterior, medial and direct distances were 1.4 ± 2.3, 2.2 ± 1.7 and 3.4 ± 1.7 mm, respectively. ΔMJS had a significant positive correlation with the medial (r = 0.580, p < 0.001) and direct (r = 0.559, p < 0.001) distances, while ΔMME had a significant positive correlation with direct distance (r = 0.295, p = 0.030). Several clinical scores were significantly negatively correlated with these distances. Conclusion: In transtibial pullout repair for MMPRTs, accurate tibial tunnel position delayed the progression of MJS narrowing and MME, leading to improved clinical outcomes. The progression of MJS narrowing was associated with the mediolateral direction of the tibial tunnel position, while the clinical scores were associated with the anteroposterior direction of the tibial tunnel position. These findings indicate the need to orient the tip of the guide in a more posterolateral direction when creating the tibial tunnel. Level of Evidence: Level IV. [ABSTRACT FROM AUTHOR]

Purpose: We aimed to evaluate the longitudinal changes in medial meniscus extrusion (MME) and clinical scores at multiple time points up to 3 years after pullout repair for medial meniscus posterior root tears (MMPRTs). Methods: This retrospective case series study included 64 patients who underwent pullout repair for MMPRTs and four MRI evaluations (preoperatively and at 3 months, 1 year, and 3 years postoperatively). MME was measured during the same time points. Clinical scores were assessed four times: preoperatively and at 1, 2, and 3 years postoperatively. Additionally, a multivariate analysis was performed on the change in MME (ΔMME) from the preoperative measurement point to 3 years postoperatively. Results: The ΔMME per month from the preoperative measurement point to 3 months postoperatively, from 3 months to 1 year postoperatively, and from 1 to 3 years postoperatively were 0.30, 0.05, and 0.01 mm/month, respectively. All clinical scores significantly improved 3 years postoperatively (p < 0.001). In a multiple regression analysis for ΔMME from the preoperative measurement point to 3 years postoperatively, sex significantly affected the outcome (p = 0.039). Conclusion: Following pullout repair for MMPRTs with well-aligned lower extremities, although MME progression could not be entirely prevented, the rate of progression decreased over time, and clinical scores improved. In particular, MME progressed markedly during the first 3 months postoperatively. Additionally, sex had a significant influence on MME progression, suggesting that males may be able to expand the indications of pullout repair for MMPRTs. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to compare medial meniscus extrusion (MME) in patients with partial medial meniscus posterior root tears (MMPRTs) through magnetic resonance imaging (MRI) conducted at two-time points and to determine whether patient characteristics or MME measurements differ in patients who respond to nonoperative treatment compared with those who require surgical treatment. Methods: Thirty-seven patients with partial MMPRTs underwent two MRI scans during nonoperative management or before pull-out repair. Among these, 17 patients received nonoperative management, and 20 underwent pull-out repair. Partial MMPRTs were diagnosed based on the MRI findings. MME measurements were performed on both MRI scans. Statistical and receiver operating curve (ROC) analyses were performed. Results: The duration between the two MRI scans was significantly shorter in the pull-out repair group than in the nonoperative management group. The increase in MME (ΔMME) on MRI scans was significantly greater in the pull-out repair group than in the nonoperative management group. Linear regression analysis revealed a weak correlation between the MRI interval and ΔMME in the nonoperative management group and a moderate correlation in the pull-out repair group. In the ROC construction, the cut-off value for ΔMME that requires surgical intervention was 0.41 mm, with a sensitivity and specificity of 85.0% and 52.9%, respectively. Conclusion: Patients with partial MMPRTs requiring surgical treatment had greater MME progression in a shorter time and a time-dependent increase in MME. Therefore, a ΔMME of ≥ 0.41 mm may be useful in deciding surgical intervention based on MRI retests. Level of evidence: III. [ABSTRACT FROM AUTHOR]

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%). [ABSTRACT FROM AUTHOR]

Purpose: Transtibial pullout repair improves the clinical outcomes of medial meniscus (MM) posterior root tears (PRTs); however, reducing MM extrusion remains challenging. Thus, the purpose of this study was to examine the role of additional posterior anchoring (PA) during pullout repair in reducing the severity of MM extrusion compared to pullout repair alone. Methods: Patients who underwent pullout repair with two-cinch stitches (TCS) only or TCS combined with PA (TCS-PA)—deployment of an additional suture anchor in the posteromedial corner of MM—were included retrospectively. MM medial and posterior extrusion (MMME and MMPE), MM extrusion and remaining volume (MMEV and MMRV), and corresponding ratios were evaluated pre-operatively and three months post-operatively using a three-dimensional meniscal model at 10° and 90° of knee flexion and compared within and between groups. Results: A total of 15 and 16 patients treated with TCS and TCS-PA, respectively, were enrolled. At 90° knee flexion, both techniques significantly reduced MMPE (TCS: 4.2 ± 0.7 mm to 3.5 ± 0.6 mm, p < 0.05; TCS-PA: 3.7 ± 0.8 mm to 2.8 ± 0.7 mm, p < 0.05) at three months post-operatively. TCS-PA reduced MMPE more significantly than TCS alone (p < 0.05). Only TCS-PA significantly improved the MMEV and MMRV ratios (39.6 ± 8.9% to 28.1 ± 6.0%, p < 0.05 and 60.4 ± 8.9% to 71.9 ± 6.0%, p < 0.05, respectively). Significance was not found in all other comparisons. Conclusions: Both techniques improved MMPE at knee flexion at the three month follow-up, with TCS-PA providing significantly superior results. Our findings support the evidence that the application of PA may be an effective surgical option for alleviating persistent MMPE. [ABSTRACT FROM AUTHOR]

Purpose: The extent to which arthropathic changes progress after medial meniscus posterior root tear (MMPRT) repair remains controversial. This retrospective study assessed medial joint space (MJS) narrowing progression after pullout repair for MMPRT and identified the correlating factors. Methods: We included 56 patients who underwent pullout repair for MMPRT. The MJS of the bilateral knees was assessed with radiography using the fixed-flexion view. A second-look arthroscopy was performed one year post-operatively for all patients. The baseline characteristics, clinical scores, Kellgren–Lawrence (KL) grade, and medial meniscus extrusion (MME) were identified. Statistical comparisons and correlation analyses were conducted. Results: The MJS narrowing width was significantly larger in MMPRT knees than in contralateral knees (0.51 ± 0.85 mm vs. 0.09 ± 0.49 mm, p < 0.001). KL grade progression was observed in 23.2% (13/56) of patients. There was a significant difference between pre- and post-operative MME values, indicating MME progression (p < 0.001). Each clinical score showed significant improvement one year post-operatively (p < 0.001). Positive correlations were found between MJS narrowing and pre-operative MJS (coefficient = 0.510, p < 0.001), rate of change in MJS (coefficient = 0.929, p < 0.001), and increase in MME (ΔMME) (coefficient = 0.506, p < 0.001). Conclusion: Knees that underwent pullout repair for MMPRT showed progression of MJS narrowing by 0.51 mm at one year post-operatively, although clinical scores markedly improved. Correlating factors for MJS narrowing were pre-operative MJS, rate of change in MJS, and ΔMME. Preventing MME progression is essential for preventing arthropathic changes. [ABSTRACT FROM AUTHOR]

Background: This study aimed to assess quadriceps muscle strength after medial meniscus (MM) posterior root repair and determine its relationship with clinical scores and MM extrusion (MME). Methods: Thirty patients who underwent pullout repair for MM posterior root tear and were evaluated for quadriceps muscle strength preoperatively and at 1 year postoperatively were included in this study. Quadriceps muscle strength was measured using the Locomo Scan-II instrument (ALCARE, Tokyo, Japan). MME and clinical scores (i.e., Knee Injury and Osteoarthritis Outcome Score [KOOS], International Knee Documentation Committee score, Lysholm score, Tegner score, and visual analog scale pain score) were evaluated preoperatively and at 1 year postoperatively, and second-look arthroscopy was performed at 1 year postoperatively. Wilcoxon's signed-rank test was used to compare each measure pre- and postoperatively. Pearson's correlation coefficient was used to assess the correlation with quadriceps muscle strength values. Multiple regression analysis was performed to identify factors associated with the change in MME (ΔMME). Results: Second-look arthroscopy confirmed continuity of the posterior root in all patients. The quadriceps muscle strength measured at 1 year postoperatively (355.1 ± 116.2 N) indicated significant improvement relative to the quadriceps muscle strength measured preoperatively (271.9 ± 97.4 N, p < 0.001). The MME at 1 year postoperatively (4.59 ± 1.24 mm) had progressed significantly relative to the MME preoperatively (3.63 ± 1.01 mm, p < 0.001). The clinical scores at 1 year postoperatively were improved significantly relative to the scores preoperatively (p < 0.001). The postoperative quadriceps muscle strength was correlated with ΔMME (correlation coefficient = -0.398, p = 0.030), and the change in quadriceps muscle strength was correlated with the KOOS-Quality of Life (correlation coefficient = 0.430, p = 0.018). Multiple regression analysis showed that the postoperative quadriceps muscle strength had a significant effect on ΔMME even when the body mass index and time from injury to surgery were included. Conclusions: After MM posterior root repair, patients with greater quadriceps muscle strength showed less MME progression. In addition, patients with greater improvement in quadriceps muscle strength had better clinical scores; therefore, continued rehabilitation aimed at improving quadriceps muscle strength after MM posterior root repair is recommended. Level of evidence: IV [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to compare the clinical outcomes of different subtypes of type 2 medial meniscus posterior root tears following transtibial pullout repair. Methods: In total, 147 patients (mean age: 66.2 ± 8.3 years) who were diagnosed with type 2 medial meniscus posterior root tears and underwent transtibial pullout repair were included. Patients were divided into 2A (n = 31), 2B (n = 90), and 2C (n = 26) groups according to tear type. Clinical outcomes were assessed pre-operatively and at second-look arthroscopy using the Knee injury and Osteoarthritis Outcome Score. The meniscal healing status was evaluated at second-look arthroscopy. Medial meniscus extrusion was calculated using magnetic resonance imaging pre-operatively and at second-look arthroscopy. Results: No significant differences in pre-operative or post-operative clinical scores were observed between each subtype, although clinical scores improved post-operatively for each subtype. Significant differences were noted in the anteroposterior width of the bridging tissues at second-look arthroscopy (2A, 7.1 ± 1.2; 2B, 6.2 ± 1.7; and 2C, 6.2 ± 1.7 mm; p = 0.045); type 2A tears were the widest. There was a significant difference in post-operative medial meniscus extrusion (2A, 3.2 ± 0.9; 2B, 4.0 ± 1.2; and 2C, 4.0 ± 1.4 mm; p = 0.004) and its progression (2A, 0.7 ± 0.6; 2B, 1.2 ± 0.8; and 2C, 1.2 ± 0.8 mm; p = 0.008), and type 2A tears were the shortest. Conclusion: Although there was no significant difference in the post-operative clinical scores among different type 2 tears in the short term, type 2A tears showed better healing and medial meniscus extrusion progression prevention, thus indicating the usefulness of classifying tear type in estimating post-operative outcomes. Level of Evidence: III. [ABSTRACT FROM AUTHOR]

Purpose: Medial meniscus (MM) posterior root tears (PRTs) lead to abnormal kinematic changes in the knee and may induce pathological external rotation of the tibia during knee flexion. This study aimed to investigate changes in the length and inclination of the anterior cruciate ligament (ACL) after MM posterior root repair using magnetic resonance imaging (MRI). Methods: This retrospective study included 44 patients who underwent MM posterior root repair between 2016 and 2019. Clinical outcomes were evaluated before and after surgery. MRI examinations were performed at 10°/90° of knee flexion preoperatively and 3 months postoperatively. The ACL length, proximal angle, and distal angle were determined using the sagittal view. MM extrusion and ACL inclination angle were determined using the coronal view. Results: Clinical outcomes significantly improved 1 year after surgery. The postoperative ACL length (29.7 ± 2.4 mm) and proximal angle (47.0 ± 7.4°) at 90° of knee flexion decreased relative to the preoperative values (31.5 ± 2.3 mm and 51.8 ± 8.7°, P < 0.01). The postoperative ACL inclination (64.9 ± 5.6°) at 10° of knee flexion decreased relative to the preoperative value (69.7 ± 5.6°, P < 0.01). Conclusion: Pathologically-stretched linear ACL at 90° of knee flexion and a steep ACL inclination at 10° of knee flexion could be reduced after MM posterior root repair. This suggests that pullout repair could restore MM function as a secondary stabilizer, thereby preventing meniscal and cartilage degeneration. [ABSTRACT FROM AUTHOR]

Purpose: Medial meniscus posterior root tears (MMPRTs) occur most frequently in middle-aged and older adults. However, this serious condition can also occur in younger patients. The purpose of this study was to compare anterior cruciate ligament (ACL) degeneration and sagittal medial tibial slope in young adults with and without MMPRT. Methods: Eighteen healthy volunteers, 18 young patients (20–49 years of age), and 30 middle-aged and older patients (50–70 years of age) with MMPRT repair were included in the study. Sex, body mass index (BMI), femorotibial angle, ACL degeneration, and medial tibial slope angle were compared among the groups. ACL degeneration and medial tibial slope angle were assessed using magnetic resonance imaging. Results: In the healthy volunteer group, the young patient group, and the older patient group, the medial tibial slopes were 3.5° ± 1.4°, 6.1° ± 2.7°, and 7.2° ± 1.9°, respectively, and the ACL degeneration rates were 5.6%, 38.9%, and 43.3%, respectively. Young patients with MMPRT had significantly steeper medial tibial slopes and ACL degeneration compared to those of the healthy volunteers (P < 0.05). The parameters of young patients were similar to those of older patients with MMPRT. In the multivariate logistic regression analysis, BMI, medial tibial slope, and ACL degeneration were significantly associated with MMPRT in young patients. Conclusion: BMI, steep medial tibial slope, and ACL degeneration contribute to MMPRT development in younger patients. Level of evidence: Level III. [ABSTRACT FROM AUTHOR]

Background: There are no recommendations for specific suture materials in transtibial pullout repair of medial meniscus posterior root tears. This study aimed to evaluate the clinical outcomes of transtibial pullout repair of medial meniscus posterior root tears using ultrahigh-molecular-weight polyethylene sutures and suture tape. Methods: We retrospectively reviewed the data of 36 patients (27 women and 9 men, mean age 64.1 years) who had undergone transtibial pullout repair of medial meniscus posterior root tears between November 2018 and December 2019. Two groups of 18 patients each received either two different cord-like sutures or suture tape. Clinical parameters were assessed preoperatively and on second-look arthroscopy (mean postoperative period 12 months). The meniscal healing status was assessed using a previously published scoring system (ranging from 0 to 10), and the incidence rate of suture cut-out was assessed on second-look arthroscopy. Results: All clinical scores significantly improved in both groups, with no significant between-group differences on second-look arthroscopy. The arthroscopic meniscal healing scores significantly differed between sutures (mean 6.7 points) and suture tape (mean 7.4 points; p = 0.044). No significant between-group difference in the suture cut-out rate was observed. Conclusions: This study found no significant differences in the clinical outcomes between ultrahigh-molecular-weight polyethylene sutures and suture tape. Favorable clinical outcomes were obtained using both types of suture; however, the usefulness of suture tape appears to be limited. [ABSTRACT FROM AUTHOR]

Previous studies have noted distinctions between medial meniscus posterior root and horn cells. However, the characteristics of root remnant cells have not been explored in detail. The purpose of this study was to evaluate the gene expression levels, proliferation, and resistance to mechanical stress of remnant and horn cells. Medial meniscus tissue samples were obtained from patients who underwent total or uni-compartmental knee arthroplasty. Cellular morphology, sry-type HMG box 9, type II collagen, and chondromodulin-I gene expression levels were analyzed. Collagen synthesis was assessed by immunofluorescence staining. Proliferation analysis after 4 h-cyclic tensile strain was performed. Horn cells displayed triangular morphology, whereas root remnant cells appeared fibroblast-like. sry-type HMG box 9 mRNA expression levels were similar in both cells, but type II collagen and chondromodulin-I mRNA expressions were observed only in horn cells. The ratio of type II collagen-positive cells in horn cells was about 10-fold higher than that in root remnant cells, whereas the ratio of sry-type HMG box 9-positive cells was similar. A significant increase in proliferation was observed in root remnant cells compared to that in horn cells. Further, under cyclic tensile strain, the survival rate was higher in root remnant cells than in horn cells. Medial meniscus root remnant cells showed higher proliferation and resistant properties to cyclic tensile strain than horn cells and showed no chondromodulin-I expression. Preserving the medial meniscus posterior root remnant during pullout repair surgery might maintain mechanical stress-resistant tissue and support healing. [ABSTRACT FROM AUTHOR]

Background: Diagnosing partial tears of the medial meniscus (MM) posterior root is difficult. The aim of this study was to evaluate diagnostic values involved in conventional magnetic resonance imaging (MRI) features of MM posterior root tears (MMPRTs) and find other MRI-based findings in patients with partial MMPRTs. Methods: Eighteen patients who had arthroscopically confirmed partial MMPRTs were included. As a control, 18 patients who underwent partial meniscectomy for other types of MM tears were evaluated. Isolated partial MMPRTs were classified into the following three types: type A, accurate partial stable tear (cleavage < 1/2 of root width); type B, bridged unstable root tear (cleavage ≥ 1/2 of root width); type C, complex horn tear expanded to the root. Conventional MRI-based findings of MMPRTs were evaluated between two groups (n = 23). Posterior root irregularity, bone marrow spot, and ocarina-like appearance showing several condensed circles in triangular meniscal horn (ocarina sign) were also evaluated. Results: Posterior root irregularity and bone marrow spot were frequently observed in the partial MMPRTs (47.8%), compared with the other MM tears (P = 0.007 and 0.023, respectively). The ocarina sign was detected in 69.6% of patients with partial MMPRTs. A significant difference between two groups was observed in a positive ratio of ocarina sign (P < 0.001). Types A, B, and C of the partial tear/damage were observed in three, eight, and seven patients, respectively. The ocarina sign was the most common MRI finding in each type of partial MMPRT. Conclusions: This study demonstrated that a characteristic MRI finding, "ocarina sign," was frequently observed in patients with partial tear/damage of the MM posterior root. The ocarina sign was the most common MRI finding in several types of partial MMPRTs. Our results suggest that the ocarina sign may be useful to diagnose unnoticed partial MMPRTs. Level of evidence: IV, retrospective comparative study. [ABSTRACT FROM AUTHOR]

Purpose: Medial meniscus posterior root tears (MMPRTs) can cause severe medial extrusion of the medial meniscus (MMME) and the progression of knee degenerative changes, inducing a high signal intensity of the meniscus on magnetic resonance imaging (MRI). Although MMME and intrameniscal signal intensity (IMSI) reportedly decreased within 3 months after MMPRT repair, no previous studies have reported these changes after a 1-year follow-up. This study aimed to investigate the 1-year postoperative changes in MMME and IMSI on MRI after using different suture techniques. Methods: Overall, 33 patients with MMPRT were evaluated, 22 underwent FasT-Fix-dependent modified Mason–Allen suture (F-MMA) repair, and 11 underwent two simple stitches (TSS) repair. MRI examinations were performed preoperatively and 1 year postoperatively. MMME and IMSI were determined using MRI. Results: A significant decrease in postoperative MMME was observed in the TSS group (4.1 ± 1.0) relative to that in the F-MMA group (5.1 ± 1.4, P = 0.03). A significant decrease in postoperative IMSI (0.75 ± 0.14) was observed relative to preoperative IMSI in the TSS group (P < 0.01), whereas postoperative IMSI (0.94 ± 0.25) was similar to preoperative IMSI in the F-MMA group (P = 0.06). Furthermore, a significant decrease in postoperative IMSI was observed in the TSS group relative to that in the F-MMA group (P < 0.01). Conclusions: The most important finding of this study is that TSS repair yielded a greater decrease in MMME and IMSI than F-MMA repair in patients with MMPRT. These results suggest that TSS repair is more useful for restoring loading stress to the posterior horn of the medial meniscus. [ABSTRACT FROM AUTHOR]

Purpose: Contralateral medial meniscus posterior root tear (MMPRT) can sometimes occur after primary surgeries for MMPRT and lead to unsatisfactory outcomes. The incidence rate and risk factors for contralateral MMPRT have not been well investigated, despite their clinical importance. Therefore, the incidence and predictors of bilateral MMPRT were aimed to be evaluated. Methods: Fourteen patients with bilateral MMPRT (group B) and 169 patients with unilateral MMPRT (group U) were enrolled in this study. Sex, age, body mass index, time between injury and surgery, and medial tibial slope angle (MTSA) were compared between the groups. MTSA was measured using lateral radiographs. Results: The incidence rate of bilateral MMPRT was 6.2% among all patients with MMPRTs. Multivariate logistic regression analysis showed that a prolonged time between injury and surgery (odds ratio [OR], 1.0; 95% confidence interval [CI] 1.00–1.01; P < 0.05) and steeper MTSA (OR, 1.85; 95% CI 1.21–2.64; P < 0.01) were significantly associated with the development of bilateral MMPRT. Receiver operating characteristic curve analysis showed that MTSA > 10.0° was associated with bilateral MMPRT, with a sensitivity of 93% and specificity of 69%. Conclusion: A longer time between injury and surgery and steeper MTSA were risk factors for the development of bilateral MMPRT. Surgeons need to pay close attention to the contralateral knee in addition to the primary injured knees when treating knees with steep MTSA. Besides, early meniscal repair of primary MMPRT would be important to prevent the events of contralateral MMPRT. Level of evidence: III. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose/Aim of the study: Posterior root injury of the medial meniscus often leads to articular cartilage degeneration due to altered biomechanics. To avoid dysfunction, the attachment must be repaired using the transtibial pullout technique. To guide appropriate placement of the tibial tunnel, additional details on the normal anatomy of the meniscus insertion are needed. Therefore, we performed a histological analysis of a tibial bone slice with the medial meniscus posterior insertion obtained during total knee arthroplasty surgery. Materials and methods: Horizontal slices of the proximal tibia were obtained from 7 patients with osteoarthritis who underwent total knee arthroplasty. After decalcification, the region of the posterior horn was cut out and segmented into four pieces (2.0 mm thickness; medial to lateral). Sagittal sections were evaluated by safranin O staining or immunohistochemistry with anti-type collagen antibody. Results: Safranin O staining showed that the insertion of the posterior root consisted primarily of fibrocartilaginous layers in segment 2. Anatomically, segment 2 corresponded to the sagittal plane passing through the peak of the medial intercondylar tubercle. In this section, safranin O staining and immunohistochemistry revealed that the anterior one-third of the posterior root insertion was richer in proteoglycans and type II collagen than the central and posterior one-third. Conclusions: Anatomical insertion of the posterior root of the medial meniscus was located at the sagittal plane passing through the peak of the medial intercondylar tubercle. The structure of the medial meniscus posterior insertion was mainly localized in the anterior one-third. [ABSTRACT FROM AUTHOR]

Purpose: Transtibial repair of a medial meniscus posterior root tear (MMPRT) can improve clinical outcomes, although meniscal extrusion remains. However, few studies have investigated the volume of meniscal extrusion. This study aimed to evaluate the effect of transtibial repair in reducing the volume using three-dimensional (3D) magnetic resonance imaging, at 10° and 90° knee flexion. Methods: Twenty patients with MMPRTs and 16 volunteers with normal knees participated. The 3D models of meniscus were constructed using SYNAPSE VINCENT®. The meniscal extrusion and its volume were measured at 10° and 90° knee flexion. Differences between the pre- and postoperative examinations were assessed using the Wilcoxon signed-rank test. The postoperative parameters were compared to those in patients with normal knees. Results: There were no significant pre- and postoperative differences in any parameter at 10° knee flexion. At 90° knee flexion, the posterior extrusion and its meniscal volume were decreased significantly after transtibial repair (p < 0.05), even though these parameters were larger than in the normal knees. On the other hand, intra-articular meniscal volume calculated by the extrusion volume was increased to the level of the normal knee. Conclusions: This study demonstrated that transtibial repairs improved the intra-articular/intra-tibial surface volume of the medial meniscus by reducing the posteromedial extrusion during knee flexion. This 3D analysis is clinically relevant in evaluating that, while transtibial root repair has a limited ability to reduce meniscal extrusion, it can restore the functional volume of the medial meniscus which contributes to the shock absorber postoperatively. Level of evidence: IV. [ABSTRACT FROM AUTHOR]

Purpose: To investigate changes in meniscal extrusion during knee flexion before and after pullout fixation for medial meniscus posterior root tear (MMPRT) and determine whether these changes correlate with articular cartilage degeneration and short-term clinical outcomes.Methods: Twenty-two patients (mean age 58.4 ± 8.2 years) diagnosed with type II MMPRT underwent open magnetic resonance imaging preoperatively, 3 months after transtibial fixation and at 12 months after surgery, when second-look arthroscopy was also performed. The medial meniscus medial extrusion (MMME) and the medial meniscus posterior extrusion (MMPE) were measured at knee 10° and 90° flexion at which medial meniscus (MM) posterior translation was also calculated. Articular cartilage degeneration was assessed using International Cartilage Research Society grade at primary surgery and second-look arthroscopy. Clinical evaluations included Knee Injury and Osteoarthritis Outcome Score, International Knee Documentation Committee subjective knee evaluation form, Lysholm score, Tegner activity level scale, and pain visual analogue scale.Results: MMPE at 10° knee flexion was higher 12 months postoperatively than preoperatively (4.8 ± 1.5 vs. 3.5 ± 1.2, p = 0.01). MMPE at 90° knee flexion and MM posterior translation were smaller 12 months postoperatively than preoperatively (3.5 ± 1.1 vs. 4.6 ± 1.3, 7.2 ± 1.7 vs. 8.9 ± 2.0, p < 0.01). Articular cartilage degeneration of medial femoral condyle correlated with MMME in knee extension (r = 0.5, p = 0.04). All clinical scores significantly improved 12 months postoperatively. However, correlations of all clinical scores against decreased MMPE and increased MMME were not detected.Conclusions: MMPRT transtibial fixation suppressed the progression of MMPE and cartilage degeneration and progressed MMME minimally in knee flexion position at 1 year. However, in the knee extension position, MMME progressed and correlated with cartilage degeneration of medial femoral condyle. MMPRT transtibial fixation contributes to the dynamic stability of the MM in the knee flexion position.Level Of Evidence: IV. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to clarify the advantages of three-dimensional (3D) magnetic resonance imaging (MRI) over two-dimensional (2D) MRI in measuring the size of the medial meniscus (MM) and to analyse the volumes of MM and the extruded meniscus in patients with MM posterior root tear (MMPRT), at 10° and 90° knee flexion.Methods: This study included 17 patients with MMPRTs and 15 volunteers with uninjured knees. The MMs were manually segmented for 3D reconstruction; thereafter, the extruded part separated from the tibial edge was determined. The length, width, height, and extrusion of MM were measured by the 2D and 3D methods, and compared. The MM volume, extruded meniscus volume, and their ratio were also calculated using 3D analysis software in the two groups.Results: The estimated length and posterior height of MM were larger with 3D MRI than with 2D MRI measurements. The MM volume was significantly greater in MMPRT knees than in normal knees, with increasing MM height. In MMPRT knees, the mean volume of the extruded meniscus and its ratio significantly increased by 304 mm3 (p = 0.02) and 9.1% (p < 0.01), respectively, during knee flexion.Conclusions: This study demonstrated that 3D MRI could estimate the precise MM size and that MMPRT caused swelling of the meniscus due to the increased thickness in the posteromedial part. The clinical significance of this study lies in its 3D evaluation of MM volume, which should help the surgeon understand the biomechanical failure of MM function and improve MMPRT repair technique.Level Of Evidence: III. [ABSTRACT FROM AUTHOR]

The medial meniscus (MM) posterior root has important functions in preventing an excessive loading stress during knee motion and degeneration of the articular cartilage. Although the transtibial pullout repair has become the gold standard for MM posterior root tears (MMPRTs), MM extrusion remains. In addition, during knee extension to deep flexion, the MM posterior segment in the MMPRT knee has been shown to translate toward the posteromedial direction, causing a notable MM posterior extrusion. Thus, the reduction in the MM posteromedial extrusion is one of the important postoperative outcomes to restore the meniscal function and eventually prevent the progression of knee osteoarthritis. The present technical note describes an arthroscopic technique addition to the pullout repair, in which an all-inside suture is inserted into the posteromedial part of the MM to reduce the MM posteromedial extrusion. [ABSTRACT FROM AUTHOR]

Purpose: Medial meniscus posterior root tear (MMPRT) leads to a rapid degradation of articular cartilage. In the treatment of MMPRT, transtibial pullout repair demonstrates a high clinical survival rate. However, there is no reliable method to evaluate the meniscal healing after surgery. We propose an arthroscopic scoring system for evaluating the meniscal healing status. The aim of this study was to investigate the correlations between second-look arthroscopic scores and clinical outcomes after transtibial pullout repair. Methods: Twenty patients who had MMPRTs underwent transtibial pullout repairs. Clinical outcomes were assessed using the Japanese Knee Injury and Osteoarthritis Outcome Score (KOOS) and pain score evaluated by visual analogue scale at preoperatively and 1 year postoperatively. The healing status of repaired MM was assessed at one year post-operatively using a semi-quantitative arthroscopic scoring system (total, 10 points) composed of three evaluation criteria: (i) anteroposterior width of bridging tissues, (ii) stability of the MM posterior root, and (iii) synovial coverage of the sutures. Linear regression analysis was used to assess the correlation between second-look arthroscopic scores and clinical outcomes. Results: Transtibial pullout repairs of MMPRTs significantly improved clinical evaluation scores at one year post-operatively. A median of second-look arthroscopic scores was 6.5 (5.75–8). A good correlation was observed between the arthroscopic score and KOOS quality of life (QOL) subscale. A moderate negative correlation between the arthroscopic score and pain score was observed. Conclusions: This study demonstrated that our semi-quantitative scoring system of meniscal healing correlated with the KOOS QOL subscale following MMPRT transtibial pullout repair. Our results suggest that the second-look arthroscopic score using this system may be a useful scale to determine and compare the healing status of the MM posterior root. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to evaluate the shape and shift of the medial meniscus before and after meniscal repair concurrent with anterior cruciate ligament (ACL) reconstruction using magnetic resonance imaging (MRI) at 90° of knee flexion.Methods: This study included 18 patients with ACL-deficient knees without meniscus tears (group A), 11 patients with medial meniscus tears alone (group M), and 15 patients with ACL-deficient knees complicated with medial meniscus tears (group AM). The posterior segment shape was evaluated using open MRI at 90° of knee flexion preoperatively and at 3 months postoperatively. The length, height, width, and posterior extrusion of the medial meniscus and posterior tibiofemoral distance were measured. These measurements were compared between the three groups.Results: On preoperative MRI, a significant difference was observed in the posterior extrusion of the medial meniscus (group A, 1.2 ± 0.5 mm; group M, 1.7 ± 0.3 mm; group AM, 4.1 ± 1.5 mm, p < 0.001). All parameters did not differ between the three groups on postoperative MRI. In addition, the posterior width and extrusion of the medial meniscus were decreased significantly after meniscal repair concurrent with ACL reconstruction.Conclusions: This study demonstrated that the medial meniscus shifted posteriorly at 90° of knee flexion in ACL-deficient knees complicated with medial meniscus tears. Medial meniscal repair concurrent with ACL reconstruction improved the deformed morphology and posterior extrusion. MRI measurements of the posterior extrusion at the knee-flexed position may be clinically useful to assess the functional improvement of the medial meniscus following meniscal repair combined with ACL reconstruction.Level Of Evidence: III. [ABSTRACT FROM AUTHOR]

ABSTRACT: This study aimed to evaluate the relationship between preoperative lateral meniscal extrusion (LME) and arthroscopic findings of lateral meniscus posterior root tear (LMPRT) in knees with anterior cruciate ligament (ACL) tear. Thirty‐five knees that had LMPRTs with concomitant ACL tears on arthroscopy were evaluated. Patients were divided into two groups, partial and complete root tears, via arthroscopic findings at the time of ACL reconstruction. For comparison, we added two groups, using the same database; 20 normal knees (normal group) and 20 ACL‐injured knees without LM injury (intact LM group). We retrospectively measured preoperative LMEs using magnetic resonance imaging (MRI). Twenty‐three knees had partial LMPRTs. Complete LMPRTs were observed in 12 knees. The average LME was −0.1 ± 0.4 mm in the normal group, 0.2 ± 0.5 mm in the intact LM group, 0.4 ± 0.8 mm in the partial LMPRT group, and 2.0 ± 0.6 mm in the complete LMPRT group. A significant difference in preoperative LMEs was observed between the complete LMPRT group and the other groups (p < 0.001). The receiver operating curve analysis, which distinguishes a partial tear from a complete tear, identified an optimal cut‐off point of 1.1 mm for preoperative LME. This LME cut‐off had a sensitivity of 100% and specificity of 83% for complete LMPRT. We found that preoperative LMEs were larger in complete LMPRTs associated with ACL injuries than in partial LMPRTs. Our results suggest that preoperative MRI‐detected LME may be a useful indicator for estimating LMPRT severity in ACL‐injured knees. Level of evidence: Retrospective comparative study level IV. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1894–1900, 2018. [ABSTRACT FROM AUTHOR]

Purpose: Anterior cruciate ligament (ACL) reconstruction can reduce the risk of developing osteoarthritic knees. The goals of ACL reconstruction are to restore knee stability and reduce post-traumatic meniscal tears and cartilage degradation. A chronic ACL insufficiency frequently results in medial meniscus (MM) injury at the posterior segment. How ACL reconstruction can reduce the deformation of the MM posterior segment remains unclear. In this study, we evaluated the form of the MM posterior segment and anterior tibial translation before and after ACL reconstruction using open magnetic resonance imaging (MRI).Methods: Seventeen patients who underwent ACL reconstructions without MM injuries were included in this study. MM deformation was evaluated using open MRI before surgery and 3 months after surgery. We measured medial meniscal length (MML), medial meniscal height (MMH), medial meniscal posterior body width (MPBW), MM-femoral condyle contact width (M-FCW) and posterior tibiofemoral distance (PTFD) at knee flexion angles of 10° and 90°.Results: There were no significant pre- and postoperative differences during a flexion angle of 10°. At a flexion angle of 90°, MML decreased from 43.7 ± 4.5 to 41.4 ± 4.5 mm (P < 0.001), MMH from 7.5 ± 1.4 to 6.9 ± 1.4 mm (P = 0.006), MPBW from 13.1 ± 2.0 to 12.2 ± 1.9 mm (P < 0.001) and M-FCW from 10.0 ± 1.5 to 8.5 ± 1.5 mm (P < 0.001) after ACL reconstruction. The PTFD increased from 2.1 ± 2.8 to 2.7 ± 2.4 mm after ACL reconstruction (P = 0.015).Conclusions: ACL reconstruction affects the contact pattern between the MM posterior segment and medial femoral condyle and can reduce the deformation of the MM posterior segment in the knee-flexed position by reducing abnormal anterior tibial translation. It possibly prevents secondary injury to the MM posterior segment and cartilage that progresses to knee osteoarthritis.Level Of Evidence: IV. [ABSTRACT FROM AUTHOR]

Purpose/Aim of the Study: Inner meniscus cells have a chondrocytic phenotype, whereas outer meniscus cells have a fibroblastic phenotype. In this study, we examined the effect of hyaluronan on chondrocytic gene expression in human meniscus cells.Materials and Methods: Human meniscus cells were prepared from macroscopically intact lateral meniscus. Inner and outer meniscus cells were obtained from the inner and outer halves of the meniscus. The cells were stimulated with hyaluronan diluted in Dulbecco’s modified Eagle’s medium without serum to the desired concentration (0, 10, 100, and 1000 μg/mL) for 2–7 days. Cellular proliferation, migration, and polymerase chain reaction analyses were performed for the inner and outer cells separately. Meniscal samples perforated by a 2 mm diameter punch were maintained for 3 weeks in hyaluronan-supplemented medium and evaluated by histological analyses.Results: Hyaluronan increased the proliferation and migration of both meniscus cell types. Moreover, cellular counts at the surface of both meniscal tissue perforations were increased by hyaluronan treatments. In addition, hyaluronan stimulated α1(II) collagen expression in inner meniscus cells. Accumulation of type II collagen at the perforated surface of both meniscal samples was induced by hyaluronan treatment. Hyaluronan did not induce type I collagen accumulation around the injured site of the meniscus.Conclusion: Hyaluronan stimulated the proliferation and migration of meniscus cells. Our results suggest that hyaluronan may promote the healing potential of meniscus cells in damaged meniscal tissues. [ABSTRACT FROM PUBLISHER]

ABSTRACT The anterior root of the lateral meniscus provides functional stability to the meniscus. In this study, we evaluated the relationship between the position of the tibial tunnel and extrusion of the lateral meniscus after anterior cruciate ligament reconstruction, where extrusion provides a proxy measure of injury to the anterior root. The relationship between extrusion and tibial tunnel location was retrospectively evaluated from computed tomography and magnetic resonance images of 26 reconstructed knees, contributed by 25 patients aged 17-31 years. A measurement grid was used to localize the position of the tibial tunnel based on anatomical landmarks identified from the three-dimensional reconstruction of axial computed tomography images of the tibial plateaus. The reference point-to-tibial tunnel distance (mm) was defined as the distance from the midpoint of the lateral edge of the grid to the posterolateral aspect of the tunnel aperture. The optimal cutoff of this distance to minimize post-operative extrusion was identified using receiver operating curve analysis. Extrusion of the lateral meniscus was positively correlated to the reference point-to-tibial tunnel distance ( r2 = 0.64; p < 0.001), with a cutoff distance of 5 mm having a sensitivity to extrusion of 83% and specificity of 93%. The mean extrusion for a distance >5 mm was 0.40 ± 0.43 mm, compared to 1.40 ± 0.51 mm for a distance ≤5 mm ( p < 0.001). Therefore, a posterolateral location of the tibial tunnel aperture within the footprint of the anterior cruciate ligament decreases the reference point-to-tibial tunnel distance and increases extrusion of the lateral meniscus post-reconstruction. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1625-1633, 2017. [ABSTRACT FROM AUTHOR]

Objectives: (1) To reveal the prevalence of the bony recess (posterior dimple) and (2) to determine the position of the posterior dimple on the tibial plateau using three-dimensional computed tomography (3DCT).Materials and Methods: In this study, a retrospective review of 112 patients was performed to identify the posterior dimple and to evaluate its position on 3DCT. Magnetic resonance images (MRIs) were also used to determine the positional relationship among the posterior cruciate ligament (PCL), medial meniscus posterior insertion (MMPI), and posterior dimple.Results: The posterior dimple was observed in 100 of 112 knees (89.3%) on 3DCT. The center of the posterior dimple was 13.6 ± 0.8 mm from the medial tibial eminence apex. MRI showed that the posterior dimple separated the tibial attachment of the PCL and MMPI.Conclusion: This is the first study to discuss the prevalence and position of the bony recess in the posterior intercondylar fossa. [ABSTRACT FROM AUTHOR]

The discoid lateral meniscus (DLM) is an anatomically abnormal meniscus that covers a greater area of the tibial plateau than the normal meniscus. The DLM is classified into two types: complete (CDLM) and incomplete (ICDLM) types. In this study, we investigated the histological and cell biological characteristics of CDLM and ICDLM. The number of blood vessels, proteoglycan deposition, and collagen distribution were assessed using meniscal tissues. Collagen production was also investigated in CDLM and ICDLM cells.The intercondylar region of the CDLM had a higher number of blood vessels than the inner region of the ICDLM. Safranin O staining density and type II collagen deposition in ICDLM were higher than those in CDLM. Type II collagen-positive cells were higher in ICLDM than in CDLM. CDLM cells showed slender fibroblastic morphology, while ICDLM cells were triangular chondrocytic in shape. This study demonstrated that the intercondylar region of the CDLM showed similar properties to the outer region of the meniscus. The inner region of the ICDLM, on the other hand, differed from the intercondylar region of the CDLM. Our results suggest that the intercondylar region of the CDLM may have a high healing potential like the outer meniscus. [ABSTRACT FROM AUTHOR]

The anterior root of the lateral meniscus (LM) dives underneath the tibial attachment of the anterior cruciate ligament (ACL). Although the distinct role of meniscal attachments has been investigated, the relationship between the LM anterior insertion (LMAI) and ACL tibial insertion (ACLTI) remains unclear. This study histologically analyzed the LMAI and ACLTI. Samples were divided into four regions in an anterior-to-posterior direction. Histological measurements of these insertion sites were performed using safranin O-stained coronal sections. Distribution and signal densities of type I and II collagen were quantified. The ACLTI and LMAI formed the ACL–LM complex via fiber connections. The anterior part of the ACLTI had a widespread attachment composed of dense fibers. Attachment fibers of the LMAI became dense and wide gradually at the middle-to-posterior region. The ACL–LM transition zone (ALTZ) was observed between the LMAI and the lateral border of the ACLTI at the middle part of the ACL tibial footprint. Type II collagen density of the LMAI was higher than that of the ACLTI and ALTZ. Our results can help create an accurate tibial bone tunnel within the dense ACL attachment during ACL reconstruction surgery. [ABSTRACT FROM PUBLISHER]

ABSTRACT We previously reported that mechanical stretch regulates Sry-type HMG box (SOX) 9-dependent α1(II) collagen ( COL2A1) expression in inner meniscus cells. This study examined the role of the small Rho guanosine 5' triphosphatase Rac1 and Rho-associated kinase (ROCK) in the regulation of stretch-induced SOX9 gene expression in cultured human inner meniscus cells. COL2A1 and SOX9 gene expression was assessed by real-time PCR after application of uni-axial cyclic tensile strain (CTS) in the presence or absence of ROCK and Rac1 inhibitors. The subcellular localization of SOX9 and the Rac1 effector cyclic AMP response element-binding protein (CREB), the phosphorylation state of SOX9, Rac1 activation, and the binding of CREB to the SOX9 promoter were assessed. CTS increased the expression of COL2A1 and SOX9, which was suppressed by inhibition of Rac1. ROCK inhibition enhanced COL2A1 and SOX9 gene expression in the absence of CTS. CTS stimulated the nuclear translocation and phosphorylation of SOX9, and increased Rac1 activation. CTS also increased the binding of CREB to the SOX9 promoter. The results suggest that mechanical stretch-dependent upregulation of SOX9 by CREB in inner meniscus cells depends on the antagonistic activities of ROCK and Rac1. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1479-1486, 2014. [ABSTRACT FROM AUTHOR]

Purpose: Meniscus repair can restore meniscal function that transfers the axial compressive force to circumferential tensile strain. However, few reports have investigated the relationship between concurrent meniscus repair with acute anterior cruciate ligament (ACL) reconstruction and postoperative meniscal position. This study aimed to evaluate medial meniscal size and clinical results in patients who underwent ACL reconstruction and concomitant all-inside medial meniscus repair. Methods: Twenty patients underwent ACL reconstruction and concurrent medial meniscus repair of a peripheral longitudinal tear using the FasT-Fix meniscal repair device. Medial tibial plateau length (MTPL) and width (MTPW) were determined by radiographic images. We evaluated the Lysholm score, anteroposterior instability, meniscal healing and magnetic resonance imaging (MRI)-based medial meniscal length (MML) and width (MMW). Correlations between MRI-based meniscal size, radiographic measurement and height were investigated. Results: All patients showed complete healing of the repaired meniscus in arthroscopic evaluation. However, one patient needed a subsequent meniscus repair during the follow-up period. Lysholm score and anteroposterior instability improved significantly. A better correlation was observed between MMW and MTPW than between MML and MTPL. Concurrent all-inside medial meniscus repair with ACL reconstruction significantly increased MML percentage (%MML) (100 MML/MTPL) but did not affect MMW percentage (%MMW) (100 MMW/MTPW). Conclusions: Concurrent all-inside medial meniscus repair with ACL reconstruction had satisfactory clinical results. %MML was increased by concurrent medial meniscus repair without affecting %MMW. Our results suggest that medial meniscus repair associated with ACL reconstruction may restore meniscal function by adjusting the anteroposterior length of the torn medial meniscus. [ABSTRACT FROM AUTHOR]

The meniscus is a fibrocartilaginous tissue that plays an important role in controlling complex biomechanics of the knee. A perimeniscal capillary plexus supplies the outer meniscus, whereas the inner meniscus is composed of avascular tissue. Anti-angiogenic molecules, such as chondromodulin-I (ChM-I) and endostatin, have pivotal roles in preserving the avascularity of cartilage. However, the anti-angiogenic role of ChM-I is unclear in the meniscus. We hypothesized that the inner meniscus might maintain its avascular feature by expressing ChM-I. Immunohistochemical analyses revealed that ChM-I was mainly detected in the inner and superficial zones of the meniscus. On the other hand, endostatin distribution was similar between the inner and outer meniscus. In Western blot, ChM-I was detected only in the inner meniscus, whereas endostatin was equally observed in both inner and outer menisci. In addition, ChM-I concentration of the inner meniscus-derived conditioned medium was higher than that of the outer meniscus-derived medium. ChM-I removal from the inner meniscus-derived medium and functional blocking of ChM-I significantly increased endothelial cell proliferation. In this study, we demonstrated that the inner meniscus contained larger amounts of ChM-I, and that the inner meniscus-derived ChM-I inhibited endothelial cell proliferation. Our results suggest that ChM-I may be a key anti-angiogenic factor for maintaining the avascularity of the inner meniscus. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 538-543, 2013 [ABSTRACT FROM AUTHOR]

The intrinsic zone-specific properties of the menisci are determined by biomechanical environments. In this study, we examined mechanical stretch-dependent expression of multifunctional growth factor CYR61/CTGF/NOV (CCN) 2, and investigated the role of CCN2 in meniscus cells. Uni-axial cyclic tensile strain (CTS) was applied using a STB-140 system. CTS-induced expression of CCN2 and α1(I) collagen (COL1A1) was assessed by quantitative real-time PCR analysis. The distribution of CCN2 and Smad2/3 in stretched cells was investigated by immunohistochemical analysis. Smad2/3-dependent CCN2 transactivation was measured by luciferase reporter assay. The relationship between Smad2/3 and CTS-induced CCN2 transcription was investigated by chromatin immunoprecipitation. CTS stimulated gene expression of CCN2 and COL1A1 in inner meniscus cells, but not in outer meniscus cells. Recombinant CCN2 increased COL1A1 expression only in inner meniscus cells. CCN2 synthesis and nuclear translocalization of phosphorylated Smad2/3 in inner meniscus cells were stimulated by CTS. The CCN2 promoter activity was synergistically enhanced by overexpressed Smad3 in stretched inner meniscus cells, but was not by Smad2. Chromatin immunoprecipitation revealed that CTS increased the association between Smad3 and the Smad-binding element on the CCN2 proximal promoter in inner meniscus cells. Our results suggest that stretch-induced CCN2 may have a crucial role in regulating COL1A1 expression in the inner meniscus. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1738-1745, 2012 [ABSTRACT FROM AUTHOR]

The meniscus plays an important role in controlling the biomechanics of the knee. However, the mechanical stress-related response in meniscus cells remains unclear. We investigated mechanical stretch-regulated gene expression in human meniscus cells. Human inner and outer meniscus cells were prepared from the inner and outer halves of the lateral meniscus. The gene expressions of Sry-type HMG box (SOX) 9 and α1(II) collagen (COL2A1) were assessed by real-time PCR analyses after cyclic tensile strain (CTS) treatment (0.5 Hz, 5% stretch). The localization and phosphorylation of SOX9 were evaluated by immunohistochemical and Western blot (WB) analyses. Chromatin immunoprecipitation (IP) analysis was performed to assess the stretch-related protein-DNA complex formation between SOX9 and the COL2A1 enhancer on chromatin. Type II collagen deposition and SOX9 production were detected only in inner menisci. CTS treatments increased expression of the COL2A1 and SOX9 genes in inner meniscus cells, but not in outer meniscus cells. In addition, CTS treatments stimulated nuclear translocalization and phosphorylation of SOX9 in inner meniscus cells. Chromatin IP analyses revealed that CTS increased the association between SOX9 and its DNA-binding site, included in the COL2A1 enhancer, on chromatin. Our results indicate that inner and outer meniscus cells have different properties in mechanical stretch-induced COL2A1 expression. In inner meniscus cells, mechanical stretch may have an essential role in the epigenetic regulation of COL2A1 expression. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:468-474, 2012 [ABSTRACT FROM AUTHOR]

Meniscus cells have several distinct properties in cellular morphology and extracellular matrix production. Inner meniscus cells are considered to have more chondrocytic phenotype compared with outer meniscus cells. However, the chondrogenic property of each meniscus cell has not been elucidated in detail. In this study, we investigated the difference between human inner and outer meniscus-derived cells in extracellular matrix deposition and chondrogenic potential. Monolayer-cultured inner meniscus cells showed small and ovoid shapes though slender and fibroblastic cells were obtained from outer half of human meniscus. The syntheses of type II collagen and safranin O-stained proteoglycans were increased in chondrogenic pellets derived from inner meniscus cells, rather than in outer meniscus cell-derived pellets. On the other hand, adipogenic lipid vacuoles were equally accumulated in both inner and outer meniscus cells after adipogenic treatment. Chondrogenic treatments also enhanced the expression of chondrogenic marker genes, such as Sry-type HMG box (SOX) 9, Scleraxis, and α1(II) collagen, in inner meniscus cells. However, SOX9 expression was not increased in outer meniscus cells even after chondrogenic treatment. This study demonstrated that inner meniscus cells maintained higher chondrogenic potential compared with outer meniscus cells. Our results suggest that the difference between inner and outer meniscus cells in chondrogenic property might have an essential role in preserving a zone-specific meniscal feature. [ABSTRACT FROM AUTHOR]

Authors would like to update the changes in affiliation. Corrected version of affiliation updated here. [ABSTRACT FROM AUTHOR]

Background: Different methods are available to assess the healing status of repaired root for medial meniscus posterior root tears (MMPRT) using second-look arthroscopy. However, few studies are comparing them or validating their usefulness. Therefore, it was hypothesized that the semi-quantitative arthroscopic score might correlate more with 1-year clinical outcomes in patients with MMPRT than the qualitative evaluation.Methods: Data of 61 patients who underwent MMPRT pullout repair and second-look arthroscopy were retrospectively evaluated. The semi-quantitative arthroscopic scoring system was divided into three evaluation criteria: scores from 0 to 10 points include the width of the bridging tissue, stability of the repaired root, and synovial coverage. The qualitative evaluation was classified into 4 status; complete healing, lax healing, scar tissue healing, and failed healing according to the stability and mobility of the repaired root. Multivariate linear regression analyses were used to identify predictors of 1-year postoperative clinical outcomes, including Knee Injury and Osteoarthritis Outcome, Lysholm, or International Knee Documentation Committee scores. Spearman's correlation analysis was used to analyze the correlation between second-look arthroscopic score/qualitative evaluation and 1-year postoperative clinical outcomes. In addition, the optimal cutoff point of semi-quantitative arthroscopic score was determined by receiver operating characteristic (ROC) curve. The Mann-Whitney U test was used to compare clinical outcomes between patients with semi-quantitative arthroscopic scores ≥8 and scores <8.Results: All clinical scores significantly improved at 1 year postoperatively. A good correlation was observed between the semi-quantitative score and clinical scores, but none between qualitative evaluation and clinical scores. The optimal cutoff point of semi-quantitative second-look arthroscopic score was 8 points. Significantly, better clinical outcomes were observed in patients with semi-quantitative scores ≥8 points.Conclusions: All 1-year postoperative clinical scores were significantly improved. The semi-quantitative arthroscopic scores correlate more with 1-year clinical outcomes in patients with MMPRT than the qualitative evaluation.Level Of Evidence: IV case series study. [ABSTRACT FROM AUTHOR]

Background: Proper functioning of the meniscus depends on the composition and organization of its fibrocartilaginous extracellular matrix. We previously demonstrated that the avascular inner meniscus has a more chondrocytic phenotype compared with the outer meniscus. Inhibition of the Rho family GTPase ROCK, the major regulator of the actin cytoskeleton, stimulates the chondrogenic transcription factor Sry-type HMG box (SOX) 9-dependent α1(II) collagen (COL2A1) expression in inner meniscus cells. However, the crosstalk between ROCK inhibition, SOX9, and other transcription modulators on COL2A1 upregulation remains unclear in meniscus cells. The aim of this study was to investigate the role of SOX9-related transcriptional complex on COL2A1 expression under the inhibition of ROCK in human meniscus cells.Methods: Human inner and outer meniscus cells were prepared from macroscopically intact lateral menisci. Cells were cultured in the presence or absence of ROCK inhibitor (ROCKi, Y27632). Gene expression, collagen synthesis, and nuclear translocation of SOX9 and Smad2/3 were analyzed.Results: Treatment of ROCKi increased the ratio of type I/II collagen double positive cells derived from the inner meniscus. In real-time PCR analyses, expression of SOX9 and COL2A1 genes was stimulated by ROCKi treatment in inner meniscus cells. ROCKi treatment also induced nuclear translocation of SOX9 and phosphorylated Smad2/3 in immunohistological analyses. Complex formation between SOX9 and Smad3 was increased by ROCKi treatment in inner meniscus cells. Chromatin immunoprecipitation analyses revealed that association between SOX9/Smad3 transcriptional complex with the COL2A1 enhancer region was increased by ROCKi treatment.Conclusions: This study demonstrated that ROCK inhibition stimulated SOX9/Smad3-dependent COL2A1 expression through the immediate nuclear translocation of Smad3 in inner meniscus cells. Our results suggest that ROCK inhibition can stimulates type II collagen synthesis through the cooperative activation of Smad3 in inner meniscus cells. ROCKi treatment may be useful to promote the fibrochondrocytic healing of the injured inner meniscus. [ABSTRACT FROM AUTHOR]

Background: During transtibial pullout repair of medial meniscus (MM) posterior root tears (MMPRTs), accurate tibial tunnel creation within the anatomic MM posterior root attachment seems critical. This study aimed to evaluate the tibial tunnel position created by a newly-developed Precision guide during pullout repair of MMPRTs.Methods: In 40 patients who underwent transtibial pullout repairs, the tibial tunnel was created using the Unicorn Meniscal Root (UMR) (n = 20) or Precision guide (n = 20). Three-dimensional computed tomography images of the tibial surface were evaluated postoperatively, using Tsukada's measurement method. The expected anatomic center of the MM posterior root attachment was defined as the center of three tangential lines corresponding to anatomic bony landmarks. The expected anatomic center (AC) and the tibial tunnel center (TC) were evaluated using the percentage-based posterolateral location on the tibial surface. The difference in the mediolateral and anteroposterior percentage distance between the AC and TC was calculated, as was the absolute distance between the AC and TC.Results: The mean AC was located 77.4% posterior and 40.1% lateral. The mean TC was similar in the UMR and Precision guide groups. There was no significant difference in the mediolateral percentage distance (UMR 3.9% vs. Precision 3.6%, p = 0.405), but a significant difference was observed in the anteroposterior percentage distance (UMR 3.5% vs. Precision 2.6%, p = 0.031). The mean absolute distance between the AC and TC was 3.9 mm and 3.5 mm (UMR and Precision guide groups, respectively) (p = 0.364).Conclusions: The new Precision guide can create tibial tunnel in an optimal and stable position during pullout repair of MMPRTs. [ABSTRACT FROM AUTHOR]

Background: Medial meniscus posterior root tear (MMPRT) causes medial meniscus extrusion (MME) and leads to subchondral insufficiency fracture of the knee (SIFK). However, the progression of SIFK after MMPRT pullout repair remains unknown. This study aimed to investigate the progression of SIFK and compare clinical outcomes in patients with SIFK to those without SIFK after MMPRT pullout repair. We hypothesized that the progression of SIFK would be prevented by MMPRT pullout repair, and clinical outcomes would improve in all patients.Methods: The SIFK grade (1-4) was evaluated using T2-fat suppression magnetic resonance imaging. Thirty-eight patients without SIFK (n = 22) and with low-grade SIFK (1 and 2; n = 16) who underwent MMPRT pullout repair were included. Preoperative factors, such as the duration from injury to the time of magnetic resonance imaging/surgery (weeks), femorotibial angle (degree), MME (mm), and clinical outcomes were evaluated, as well as the progression of SIFK.Results: SIFK was identified in only 9 patients (grade 1) postoperatively. Significantly improved clinical outcomes were observed in all patients. Preoperative femorotibial angle, MME, and duration from injury to the time of magnetic resonance imaging/surgery were 177.1 ± 1.5°, 3.2 ± 1.6 mm, and 6.4 ± 7.0/10.1 ± 7.5 weeks, respectively. No significant difference in preoperative factors and clinical outcomes was observed between patients with SIFK and those without SIFK.Conclusions: MMPRT pullout repair prevented the progression of low-grade SIFK and improved clinical outcomes in all patients, although bone contusions (grade 1 SIFK) were not completely healed within 1 year. MMPRT pullout repair could be a good treatment option for optimizing clinical outcomes in patients with low-grade SIFK. [ABSTRACT FROM AUTHOR]

Background: Medial meniscus (MM) posterior root repairs show favorable clinical outcomes in patients with MM posterior root tears (MMPRTs). However, there is no useful magnetic resonance imaging (MRI) finding to determine a functionally good meniscal healing following MM posterior root repairs. We hypothesized that a characteristic postoperative MRI finding can predict a good meniscal healing following pullout repairs. The aim of this study was to investigate a clinical usefulness of several MRI findings for estimating an actual meniscal healing following MMPRT repairs.Methods: Fifty eight patients who had a posteromedial painful popping of the injured knee and underwent an arthroscopic pullout repair for the MMPRT were included. Arthroscopic meniscal healing was assessed according to the Furumatsu scoring system at 1 year postoperatively. We evaluated postoperative MRI-based meniscal healing using signal intensity, continuity, suspension bridge-like sign of the MM posterior root, and MM medial extrusion on coronal images. Postoperative clinical outcome evaluations were performed at second-look arthroscopy.Results: Twenty three patients showed good arthroscopic healing scores (≥7 points). Thirty five patients had moderate/poor arthroscopic healing scores (<7 points). At 1-year follow-up period, clinical outcome scores were significantly higher in the good healing group than in the moderate/poor healing group. A characteristic meniscal shape, termed "suspension bridge sign", was highly observed in the good meniscal healing group (83%) compared with in the moderate/poor healing group (26%, P < 0.001). High signal intensity and continuity of the MM posterior root and MM medial extrusion showed no differences between both groups.Conclusions: Our study demonstrated that the MRI-based suspension bridge sign can predict an arthroscopically favorable meniscal healing following the MM posterior root repair. The suspension bridge-like MRI finding of the MM would be a useful indicator to evaluate the actual meniscal healing in patients who underwent pullout repairs for MMPRTs. [ABSTRACT FROM AUTHOR]

Background: A complete discoid lateral meniscus (DLM) has a high risk of horizontal tear. However, cellular phenotypes and extracellular matrix organizations in complete DLMs are still unclear. The aim of this study was to investigate histological and cellular biological characteristics in both the intercondylar and central regions of complete DLM.Materials and Methods: Meniscal samples were obtained from the intercondylar and central regions of complete DLM (n = 6). Blood vessels and aggregated cell ratio were measured in each region. Depositions of type I/II collagens and safranin O-stained proteoglycans in the extracellular matrix were assessed. Experiments in gene expression, morphology, proliferation, and effect of mechanical stretch were performed using cultured cells derived from each region.Results: Blood vessel counts were significantly higher in the intercondylar region than in the central region. The ratio of aggregated cells was lower in the intercondylar region than in the central region. Deposition of type I collagen was comparable for both regions. The central region contained a larger quantity of type II collagen and safranin O staining density compared with the intercondylar region. Proliferation of the fibroblastic intercondylar cells was not affected by 5%-stretching. However, stretching treatments decreased relative proliferation of the chondrocytic central cells.Conclusions: This study demonstrated that the central region of complete DLM had different cellular properties and collagen components compared with the intercondylar region. Our results suggest that the central region of complete DLM may have a low healing potential like the inner avascular region of the meniscus. [ABSTRACT FROM AUTHOR]

Background: To compare the plain knee radiograph finding of tibial eminence width between knees with complete discoid lateral meniscus, incomplete discoid lateral meniscus, and normal lateral meniscus.Materials and Methods: The study included 27 knees with discoid lateral meniscus, including 13 knees with complete discoid lateral meniscus and 14 knees with incomplete discoid lateral meniscus. A control group of 14 knees with normal lateral meniscus was also included. Tibial eminence width and the lateral slope angle of the medial tibial eminence were assessed using plain frontal knee radiographs. Individual differences in knee size were corrected by dividing tibial eminence width by tibial width to obtain the tibial eminence width percentage.Results: Mean tibial eminence width and tibial eminence width percentage in the complete discoid lateral meniscus group was significant larger than other groups. Mean lateral slope angle in the complete discoid lateral meniscus group was significantly smaller than other groups. A tibial eminence width cut-off of 13.9 mm showed a sensitivity and specificity of 100% and 83%, respectively. A tibial eminence width percentage cut-off of 18.8% showed a sensitivity and specificity of 100% and 90%, respectively. A lateral slope angle cut-off of 27.1° showed a sensitivity and specificity of 71% and 83%, respectively.Conclusion: There were clear differences in tibial eminence width, tibial eminence width percentage, and lateral slope angle between the complete discoid lateral meniscus group and the other groups. The plain radiographic parameters identified by this study could be useful for complete discoid lateral meniscus screening.Study Design: Clinical. [ABSTRACT FROM AUTHOR]