Steep posterior slope of the medial tibial plateau and anterior cruciate ligament degeneration contribute to medial meniscus posterior root tears in young patients.

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.

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%).

Medial meniscus posterior root repair influences sagittal length and coronal inclination of the anterior cruciate ligament: a retrospective study.

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.

Large flexion contracture angle predicts tight extension gap during navigational posterior stabilized-type total knee arthroplasty with the pre-cut technique: a retrospective study.

BACKGROUND: This study aimed to determine the predictors of tight extension gap (EG) compared with the flexion gap (FG) during navigational posterior stabilized-type total knee arthroplasty using the pre-cut technique. METHODS: Nineteen patients with tight EG (defined as FG-EG ≥2 mm after pre-cut; group T) and 84 patients with an approximately equal gap (defined as FG-EG = 0-1 mm after pre-cut; group E) were enrolled. Medial tibial slope angle, hip knee ankle angle, flexion contracture angle, and active maximum flexion angle were compared between the two groups. RESULTS: The multivariate logistic regression model indicated that the probability of tight EG increased with flexion contracture angle (odds ratio, 1.13; 95% confidence interval 1.05-1.20; P ≤ 0.001). According to the receiver operating characteristic analysis, the flexion contracture angle cut-off value associated with tight EG was 15.0° (sensitivity, 85%; specificity, 78%). CONCLUSION: This study demonstrated that a large flexion contracture angle (cut-off 15.0°) was associated with tight EG after pre-cut osteotomy during posterior stabilized-type total knee arthroplasty. Awareness of this risk factor may help improve preoperative predictability of tight EGs and preparedness for additional procedures, such as soft tissue release or capsulotomy, to correct them. LEVEL OF EVIDENCE: Level III.

Medial meniscus posterior root repairs: A comparison among three surgical techniques in short-term clinical outcomes and arthroscopic meniscal healing scores.

BACKGROUND: Medial meniscus (MM) posterior root repairs lead to favorable clinical outcomes in patients with MM posterior root tears (MMPRTs). However, there are few comparative studies in evaluating the superiority among several pullout repair techniques such as modified Mason-Allen suture, simple stitch, and concomitant posteromedial pullout repair. We hypothesized that an additional pullout suture at the MM posteromedial part would have clinical advantages in transtibial pullout repairs of the MMPRTs. The aim of this study was to compare the clinical usefulness among several types of pullout repair techniques in patients with MMPRTs. METHODS: Eighty-three patients who underwent arthroscopic pullout repairs of the MMPRTs were investigated. Patients were divided into three groups using different pullout repair techniques: a modified Mason-Allen suture using FasT-Fix all-inside meniscal repair device (F-MMA, n = 28), two simple stitches (TSS, n = 30), and TSS concomitant with posteromedial pullout repair using all-inside meniscal repair device (TSS-PM, n = 25). Postoperative clinical outcomes and semi-quantitative arthroscopic meniscal healing scores (0-10 points) were evaluated at second-look arthroscopies. RESULTS: No significant differences among the three groups were observed in patient demographics and preoperative clinical scores, except for preoperative Lysholm scores. At second-look arthroscopies, there were no significant differences among the three techniques in postoperative clinical outcomes and meniscal healing scores. CONCLUSIONS: This study demonstrated that the TSS-PM pullout repair technique did not show better scores in postoperative clinical outcomes and meniscal healings compared with the F-MMA and TSS techniques. Our results suggest that the concomitant posteromedial pullout suture may have no clinical advantage in the conventional pullout repairs for the patients with MMPRTs.

Transtibial pullout repair techniques using two simple stitches for medial meniscus posterior root tear can prevent the progression of medial meniscus extrusion and obtain successful outcomes.

PURPOSE: Transtibial pullout repairs using two simple stitches (TSS) and a combination of TSS with posteromedial pullout repair (TSS + PMP) using an all-inside meniscal repair device have been reported previously for the treatment of medial meniscus (MM) posterior root tears. This study aimed to investigate the postoperative clinical outcomes of these techniques including MM extrusion (MME). METHODS: Fifty-two patients who underwent transtibial pullout repair were investigated and divided into TSS (n = 27) and TSS + PMP (n = 25) groups. The clinical outcomes were assessed using the Lysholm knee score and Knee Injury and Osteoarthritis Outcome Score 1 year postoperatively and compared between two groups. MME was measured using magnetic resonance imaging at 1 year postoperatively and compared between two groups. RESULTS: A significant improvement in each clinical score was observed in both groups, and no significant difference was seen in clinical outcomes. Moreover, no significant difference in postoperative MME was observed in both groups (TSS and TSS + PMP: 3.5 mm and 3.8 mm, respectively). Though no significant progression of MME was observed in TSS group, a significant progression of it was observed in TSS + PMP group postoperatively. CONCLUSIONS: This study demonstrated that both techniques improved clinical outcomes in the short-term postoperative period. However, MME was progressed significantly in TSS + PMP group 1 year postoperatively, which indicated that PMP might not be a useful additional procedure for reducing the postoperative MME.

A posterior shiny-corner lesion of the tibia is observed in the early phase after medial meniscus posterior root tear.

BACKGROUNDS: Medial meniscus (MM) posterior root tear (PRT) results in joint overloading and degenerative changes in the knee, and pullout repair is recommended to prevent subsequent osteoarthritis. Diagnosing MMPRT is sometimes difficult, especially in the case of an incomplete tear. A posterior shiny-corner lesion (PSCL) is reported to be useful for diagnosis, although the association between MMPRT and PSCL is unknown. This study aimed to investigate the properties of PSCL, such as the location, volume, and duration from injury to the time of MRI (duration). We hypothesized that PSCL is observed in the early phase after the MMPRT onset. METHODS: T2-weighted fat-suppression magnetic resonance imaging (MRI) was obtained from 55 patients with MMPRT preoperatively. The prevalence of the PSCL; giraffe neck, cleft, and ghost signs; severe MM extrusion (> 3 mm); and the PSCL volume were evaluated. The PSCL lesion elliptical volume (mm3) was calculated by measuring the anteroposterior, transverse, and craniocaudal dimensions. RESULTS: PSCL was observed in 34 (62%) cases. The mean volume of the PSCL was 102.0 mm3. A significantly shorter duration was observed in the PSCL-positive group (5.6 weeks) than that in the PSCL-negative group (40.9 weeks, P < 0.01), although no significant correlation was observed between the PSCL volume and duration. The sensitivity for the MMPRT was 90.5% when the cut-off duration value was 3 weeks and 81.8% when the cut-off value was 8 weeks. CONCLUSIONS: MRI examination may detect PSCL if it is performed early following MMPRT onset. Detecting PSCL may be useful in diagnosing MMPRT with high sensitivity.

Medial Meniscus Posterior Root Repair Using a Modified Mason-Allen Suture Can Prevent the Progression of Cartilage Degeneration on the Loading Surface of the Medial Compartment: A Second-Look Arthroscopic Evaluation.

The treatment of medial meniscus posterior root tears (MMPRTs) has evolved to include a variety of repair strategies. This study investigated the location of the articular cartilage degeneration during second-look arthroscopy after transtibial pullout repair with a modified Mason-Allen suture using FasT-Fix (F-MMA) in 22 patients with MMPRTs. Second-look arthroscopy was performed approximately 1 year postoperatively to eval-uate the healing status of the medial meniscus (MM). Articular cartilage degeneration was assessed using the International Cartilage Repair Society grade at primary surgery and again at second-look arthroscopy. Articular surfaces of the medial/lateral femoral condyles, the medial/lateral tibial plateaus, the patella and the trochlea were divided into several subcompartments (MF 1-9, LF 1-9, MT 1-5, LT 1-5, P 1-9, T 1-3). Clinical evaluations used the Japanese Knee Injury and Osteoarthritis Outcome, Lysholm, and International Knee Documentation Committee scores. Second-look arthroscopic findings showed complete healing of the MM posterior root in all patients. Significant differences between pullout repair and second-look arthroscopy were observed for MF 2 and 4, LF 7, and P 7. All clinical outcomes were improved. Our results indicate that this technique improves clinical outcomes postoperatively and may prevent the progression of cartilage degenera-tion on the loading surface of the medial knee compartment.

Steep medial tibial slope and prolonged delay to surgery are associated with bilateral medial meniscus posterior root tear.

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.

Accurate placement of a tibial tunnel significantly improves meniscal healing and clinical outcomes at 1 year after medial meniscus posterior root repair.

PURPOSE: A medial meniscus posterior root tear results in the loss of meniscal circumferential hoop stress and causes a pathological posteromedial extrusion of the medial meniscus. Although creating a tibial tunnel in the anatomic place improves postoperative medial meniscus posterior extrusion, no studies have evaluated the relationship between tibial tunnel position and clinical outcomes. This study aimed to evaluate how tibial tunnel positioning of medial meniscus posterior root pullout repair affects meniscal healing status and clinical outcomes. METHODS: Sixty-two patients with 64 medial meniscus posterior root tears (mean age 62.8 ± 7.9 years) who had undergone pullout repairs and second-look arthroscopies were included. All 62 patients were Lachman test negative. Three-dimensional computed tomography images of the tibial surface were evaluated using a rectangular measurement grid to assess the tibial tunnel centre and medial meniscus posterior root attachment centre. Spearman's rank correlation analysis was undertaken to determine displacement distance from the medial meniscus posterior root attachment centre to the tibial tunnel centre and a meniscal healing score, as well as clinical outcomes at 1 year post-repair. RESULTS: Tibial tunnel centres were located more anteriorly and medially than the medial meniscus posterior root attachment centre (mean distance 5.0 ± 2.2 mm). The mean meniscal healing score was 6.7 ± 1.8 of 10 possible points. The 1-year postoperative clinical scores showed significant improvement compared with preoperative scores for all the items. There was a significant negative correlation in the absolute distance between the medial meniscus posterior root attachment centre and the tibial tunnel centre with the meniscal healing score (ρ = - 0.39, p = 0.002). Furthermore, there were significant positive correlations between the distance between the medial meniscus posterior root attachment centre and the tibial tunnel centre in the mediolateral direction and patient-based clinical outcomes (ρ = 0.25-0.43, p < 0.05). CONCLUSION: Accurate placement of a tibial tunnel, especially in the mediolateral direction, significantly improved meniscal healing and clinical outcomes at 1 year following medial meniscus posterior root repair. Surgeons should create a medial meniscus posterior root tibial tunnel at the anatomic attachment with particular attention to the mediolateral position. LEVEL OF EVIDENCE: Level IV.

Transtibial pullout repair of medial meniscus posterior root tears: effects on the meniscus healing score and ICRS grade among patients with mild osteoarthritis of the knee.

PURPOSE: To assess the effects of transtibial pullout repair for medial meniscus posterior root tears (MMPRTs) among patients with early osteoarthritis of the knee as measured by the meniscus healing score and to determine whether the meniscus healing score correlates with the International Cartilage Repair Society (ICRS) grade progression. METHODS: Forty-seven patients with mild osteoarthritic knees (Kellgren-Lawrence grade ≤ 2 and varus alignment < 5°) who underwent transtibial pullout repair less than 3 months after MMPRT onset were assessed. The association between meniscus healing scores at 1 year postoperatively and cartilage damage of the medial compartment (medial femoral condyle [MFC] and medial tibial plateau [MTP]) were evaluated. The MFC was divided into six zones (A to F) and the MTP into two zones (G and H). The mean ICRS grade for each zone was compared between the primary surgery and second-look arthroscopy. The correlation between cartilage damage and meniscus healing status at the time of second-look arthroscopy in each zone was analysed. RESULTS: The mean time interval from injury to surgery was 63 days, and all clinical scores showed significant improvement. There were no significant differences in the extent of cartilage damage in areas B, C, E, or F (n.s.) for MFC or in areas G and H (n.s.) for MTP. The meniscus healing score and cartilage damage were correlated in the loading areas (B, C, E, and H; - 0.53, - 0.45, - 0.33, and - 0.38, respectively; p < 0.05). CONCLUSION: Transtibial pullout repair of MMPRTs among patients with mild osteoarthritic knees improved the clinical outcomes and showed a negative correlation between high meniscus healing scores and ICRS grades in the medial compartment loading area. This study suggests that early surgery should be undertaken for patients with mild osteoarthritic knee who develop MMPRTs. LEVEL OF EVIDENCE: Level IV.

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.

Steep posterior slope and shallow concave shape of the medial tibial plateau are risk factors for medial meniscus posterior root tears.

PURPOSE: Bone morphological factors are important for menisci. Their association with medial meniscus posterior root tears, however, has not yet been studied. This study aimed to compare sagittal medial tibial slope and medial tibial plateau depth between knees with and without medial meniscus posterior root tears. METHODS: Nine healthy volunteers, 24 patients who underwent anterior cruciate ligament reconstruction, and 36 patients who underwent medial meniscus posterior root pullout repair were included. Magnetic resonance imaging examinations were performed in the 10°-knee-flexed position. The medial tibial slope and medial tibial plateau depth were compared among the groups. RESULTS: In healthy volunteers, the anterior cruciate ligament reconstruction group, and the medial meniscus posterior root tear group, the medial tibial slopes were 3.5° ± 1.4°, 4.0° ± 1.9°, and 7.2° ± 1.9°, respectively, and the medial tibial plateau depths were 2.1 ± 0.7 mm, 2.2 ± 0.6 mm, and 1.2 ± 0.5 mm, respectively. Patients with medial meniscus posterior root tears had a significantly steep medial tibial slope and shallow medial tibial plateau concavity compared to those of healthy volunteers (P < 0.01) and the anterior cruciate ligament group (P < 0.01). In the multivariate logistic regression analysis, body mass index, medial tibial slope, and medial tibial plateau depth were significantly associated with medial meniscus posterior root tears. CONCLUSIONS: A steep posterior slope and a shallow concave shape of the medial tibial plateau are risk factors for medial meniscus posterior root tear. LEVEL OF EVIDENCE: Level III: Case-control study.

An MRI-based suspension bridge sign can predict an arthroscopically favorable meniscal healing following the medial meniscus posterior root repair.

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.

High body mass index is a risk factor for unfavorable clinical outcomes after medial meniscus posterior root repair in well-aligned knees.

BACKGROUND: Severe chondral lesions and varus knee alignment are associated with poor outcomes following transtibial pullout repair for medial meniscus posterior root tears and meniscus tear is strongly associated with body mass index. The prognostic factors in well-aligned knees (femorotibial angle < 180°) with mild chondral lesions are unknown. Therefore, we investigated the prognostic factors in these patients. We hypothesized that high body mass index would lead to poor clinical outcomes following pullout repair of medial meniscus posterior root tears. METHODS: We retrospectively reviewed the files of 28 patients who had undergone pullout repair of medial meniscus posterior root tears between October 2016 and December 2017. We recorded the baseline characteristics (age, gender, height, weight, and body mass index) and the time between injury and surgery. We recorded the International Knee Documentation Committee scores, Knee injury and Osteoarthritis Outcome Scores, and pain visual analog scale scores. Using magnetic resonance imaging preoperatively and 1 year after surgery, we measured the medial meniscus body width and absolute and relative medial meniscus extrusion. Pearson correlation and multivariate linear regression analyses were used to assess potential associations between these factors and clinical outcomes. RESULTS: Age positively correlated (coefficient = 0.49, P < 0.01) and body mass index negatively correlated with the postoperative International Knee Documentation Committee score (coefficient = -0.64, P < 0.01). In multivariate linear regression analysis, body mass index was a significant factor leading to poor postoperative International Knee Documentation Committee score (R2 = 0.29, P < 0.05). CONCLUSIONS: Body mass index > 30 kg/m2 is a risk factor for unfavorable clinical outcomes following pullout repair of medial meniscus posterior root tears in well-aligned knees. LEVEL OF EVIDENCE: III, Comparative retrospective study.

Two simple stitches for medial meniscus posterior root repair prevents the progression of meniscal extrusion and reduces intrameniscal signal intensity better than modified Mason-Allen sutures.

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.

A histological study of the medial meniscus posterior root tibial insertion.

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.

Medial meniscus posterior root tear causes swelling of the medial meniscus and expansion of the extruded meniscus: a comparative analysis between 2D and 3D MRI.

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.

Transtibial fixation for medial meniscus posterior root tear reduces posterior extrusion and physiological translation of the medial meniscus in middle-aged and elderly patients.

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.

A repair technique using two simple stitches reduces the short-term postoperative medial meniscus extrusion after pullout repair for medial meniscus posterior root tear.

BACKGROUND: Two types of repair techniques, FasT-Fix modified Mason-Allen (F-MMA) and two simple stitches (TSS), for the treatment of a medial meniscus posterior root tear (MMPRT) were previously reported. However, whether these techniques could prevent postoperative medial meniscus extrusion (MME) progression is unknown. This study investigated and compared postoperative MME of the two repair techniques. METHODS: Forty-seven knees that had undergone pullout repair for MMPRT were retrospectively reviewed. These knees were divided into two groups as follows: In 26 knees, MMPRT was treated using the F-MMA technique and fixed with the knee flexed at 45° and 20 N of tension [F-MMA (45°-20 N) group], and in 21 knees, MMPRT was treated using the TSS technique and fixed with the knee flexed at 20° and 30 N of tension [TSS (20°-30 N) group]. The medial meniscus body width (MMBW), absolute MME (aMME), and relative MME (rMME = absolute MME/MMBW) were measured and compared using magnetic resonance imaging 3 months postoperatively. The Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales for clinical outcomes were compared between the two groups at 6 months postoperatively. RESULTS: At 3 months postoperatively, the aMME and rMME significantly decreased in the TSS (20°-30 N) compared to the F-MMA (45°-20 N) group. The TSS (20°-30 N) group had better KOOS subscale scores than the F-MMA (45°-20 N) group at 6 months postoperatively. CONCLUSIONS: The TSS technique with appropriate tibial fixation can decrease MME soon after surgery. This may prevent osteoarthritis progression and improve clinical outcomes.