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

Biomechanical effects of LCWHTO vs. MOWHTO on medial meniscus posterior root repair: a finite element analysis

Whether isolated high tibial osteotomy (HTO) or HTO combined with medial meniscus posterior root (MMPR) repair is the optimal surgical treatment of MMPR tears remains controversial. This study compared the biomechanical effects of isolated HTO versus MMPR repair combined with medial open wedge HTO (MOWHTO) or lateral closed wedge HTO (LCWHTO) using finite element analysis (FEA). In this study, the MRI and CT data of the knee joint were used to create an FEA model. MOWHTO and LCWHTO simulations adjusted the mechanical axis to the Fujisawa point, with MMPR conditions simulated as intact, tear, or repaired. The ankle center was fixed and a 1000 N force was applied to the knee. In the LCWHTO models, the posterior tibial slope (PTS) decreased, whereas it increased in the MOWHTO models. Changes in the PTS following HTO influenced the stress distribution in the MMPR. HTO combined with MMPR repair showed a reduction in the maximum contact stress by 5.4-11.4% and increased contact area by 29.5-41.0% in the medial knee compartment relative to isolated HTO. This study demonstrated that MMPR repair combined with LCWHTO would be more protective against stress loading in the MMPR than MMPR repair combined with MOWHTO or isolated HTO.

Posteromedial opening wedge high tibial osteotomy has favourable outcomes in simultaneous medial meniscus posterior root repair and varus medial knee osteoarthritis patients without concomitant root tear

PURPOSE

To evaluate the radiological and clinical outcomes in two patient groups: first, varus aligned medial meniscus posterior root tear (MMPRT) patients who underwent posteromedial open wedge high tibial osteotomy (PMOWHTO) and simultaneous root repair; second, patients with varus medial knee osteoarthritis without MMPRT who underwent PMOWHTO.

METHODS

Patients had MMPRT repair concomitant with PMOWHTO and varus medial knee osteoarthritis without concomitant root tear patients who underwent PMOWHTO and were reviewed. Radiographic parameters, medial meniscus extrusion (MME) and Knee Society Scores [KSSs, including the following subscores: knee score (KS) and knee function score (KFS)] were evaluated. Continious variables are expressed as the median and interquartile range (IQR) [IQR: (Q1;Q3); Q1: median of lower half, Q3: median of upper half]. The minimum follow-up period was 24 months [29 (28;35) months].

RESULTS

A total of 36 knees of 34 patients underwent PMOWHTO were included. Patients were divided into two groups according to the presence or absence of a MMPRT. Nineteen of the 36 knees had MMPRTs, and all of them had concomitant root repair (Group 1). Seventeen of the 36 patients did not have MMPRTs (Group 2). The posterior tibial slope (PTS) decreased postoperatively in a total of 36 knees (p < 0.001). There were no significant changes in MME postoperatively in any intragroup comparison. The preoperative and follow-up MMEs of Group 1 were greater than those of Group 2 (p < 0.001). The KSs and KFSs in both Group 1 and Group 2 increased during follow-up [KS; Group 1: 43 (36;53) vs. 86 (84;95), p < 0.001. Group 2: 49 (45;57) vs. 89 (80;93), p < 0.001. KFS; Group 1: 60 (50;60) vs. 90 (80;100), p < 0.001. Group 2: 60 (50;60) vs. 80 (80;90), p < 0.001]. All knees achieved minimal clinically important difference (MCID) in terms of KSs. Eighteen (95%) knees achieved MCID in Group 1, and 17 (100%) achieved MCID in Group 2 in terms of KFSs. There were no differences between Groups 1 and 2 in terms of preoperative and follow-up KSs or preoperative KFSs. The follow-up KFSs in Group 1 was significantly greater than that in Group 2 (p = 0.032).

CONCLUSIONS

PMOWHTO has favourable clinical and radiological outcomes and prevents PTS increase in simultaneous MMPRT repair and varus medial knee osteoarthritis patients without concomitant root tear.

LEVEL OF EVIDENCE

Level IV, case series.

Differences Between Traumatic and Degenerative Medial Meniscus Posterior Root Tears: A Systematic Review

BACKGROUND

Intact meniscus roots are a prerequisite for normal meniscal function, including even distribution of compressive forces across the knee joint. An injury to the root disrupts the hoop strength of the meniscus and may lead to its extrusion and the development of osteoarthritis. A medial meniscus posterior root tear (MMPRT) is often thought to have a primary degenerative pathogenesis. However, there is mention of some cases of MMPRTs where the patients have a solely traumatic injury to a previously healthy meniscus.

PURPOSE

To describe a subpopulation of patients with traumatic MMPRT.

STUDY DESIGN

Systematic review; Level of evidence, 5.

METHODS

The Web of Science database (www.webofscience.com) was queried using the Medical Subject Headings term "medial root tear." Articles were reviewed, and those evaluated for MMPRTs in a degenerative meniscus were excluded. A total of 25 articles describing cases of acute traumatic causes were included in this study. For these articles, the patient characteristics, injury mechanisms, and concomitant injuries evaluated were recorded and pooled.

RESULTS

The search revealed 660 articles, and 25 were selected for inclusion. A total of 113 patients with a traumatic MMPRT were identified and included in this review. The study population had a mean age of 27.1 years and a high share of men (64%). Also, this review displays how most patients with traumatic MMPRTs also suffer concomitant injuries (68%).

CONCLUSION

The findings in this review support our hypothesis that there is a unique subgroup with acute traumatic MMPRTs that have unique patient characteristics, injury mechanisms, and combined injuries, compared with previously published reviews on MMPRTs.

Steeper Slope of the Medial Tibial Plateau, Greater Varus Alignment, and Narrower Intercondylar Distance and Notch Width Increase Risk for Medial Meniscus Posterior Root Tears: A Systematic Review

PURPOSE

To evaluate the available literature on the relationship between knee bony morphology and medial meniscus posterior root tears (MMPRTs) to determine which tibiofemoral morphologic risk factors may predispose the development of MMPRTs.

METHODS

Embase, MEDLINE, and PubMed databases were searched to identify all relevant human clinical studies investigating knee morphologic features and MMPRTs. Shape features were compared between control groups and patients with MMPRTs. The methodological index for nonrandomized studies (MINORS) instrument was utilized to assess the methodological quality of included studies.

RESULTS

Thirteen level III evidence studies and 1 level IV evidence study were included in this review (n = 2,181), with 895 patients in the MMPRT group and 1,286 in the control group. Tibial morphology features associated with an increased risk for MMPRTs included an increased medial tibial slope (6 studies), increased tibial torsion (1 study), increased medial meniscal slope (1 study), and shallower medial tibial plateau concavity (1 study). Varus mechanical alignment was found to increase the risk for MMPRTs (4 studies). Femoral morphology features associated with an increased risk for MMPRTs included an A-type intercondylar notch (1 study), increased medial femoral condyle (MFC) angle (1 study), narrower intercondylar distance (1 study), narrower intercondylar notch width (1 study), shorter MFC distal offset distance (1 study), increased MFC width (1 study), increased MFC to medial tibial condyle width ratio (1 study), greater distance between the medial tibial eminence and MFC (1 study), and smaller femoral offset ratios of both the medial and lateral condyles (1 study).

CONCLUSION

Multiple tibiofemoral shape features, including a steeper slope of the medial tibial plateau, greater varus alignment, and a narrower intercondylar distance and notch width, were found to be predictive factors for MMPRTs.

LEVEL OF EVIDENCE

Level IV (Systematic review of Level III and IV studies).

Biomechanical comparison of the tensile strength of fixation implants used for pull-out repair of medial meniscus posterior root tear

PURPOSE

Medial meniscus posterior root tears (MMPRT) pull-out repair aims to restore the meniscus' anatomical structure. Different implants are utilized for thread fixation in the pull-out repair technique for MMPRT. However, biomechanical evidence comparing the fixation strengths of these implants remains unavailable. This study investigated the tensile strength of three fixation implants in porcine knee models of MMPRT pull-out repair.

METHODS

This study categorized 30 porcine MMPRT models undergoing pull-out repair into three groups (10 specimens each) based on the implant utilized for fixation, including double spike plate, metallic interference screw (IFS), and resorbable IFS fixed group. A tensile tester was used to track the suture wire threaded to the medial meniscus anterior root. The displacement length was recorded after 10 and 20 loading cycles (10-30 N, 100 mm/min cross-head speed). Each specimen was then stretched to failure (50 mm/min cross-head speed), failure modes were recorded, and structural properties (maximum load, linear stiffness, elongation at failure, and elongation at yield) were compared. Fisher's exact test and one-way analysis of variance were utilized to assess the differences.

RESULTS

No significant differences in displacement length, upper yield load, maximum load, linear stiffness, elongation at yield, elongation at failure, and frequency of failure mode were observed between the three groups.

CONCLUSION

All implants were comparable in terms of fixation strength. Thus, resorbable interference screws may be particularly useful in this technique and does not require implant removal surgery.

LEVEL OF EVIDENCE

IV.

Biomechanical comparison of ultra-high molecular weight polyethylene sutures of different thicknesses of the tensile strength for pullout repair of medial meniscal posterior root tear

Purpose

Medial meniscus posterior root tears (MMPRT) are a risk factor for knee osteoarthritis. The predominant treatment for MMPRT is transtibial pullout repair, and loop suture remains the gold standard procedure. This study aimed to investigate the structural properties of the meniscus-suture-tibia (MST) complex after loop stitch using ultra-high molecular weight polyethylene (UHMWPE) suture tape of different thicknesses.

Methods

This study used 20 fresh porcine MMPRT model knees. All specimens were randomised into two treatment groups: (1) pullout repair using 1.3 mm suture tape (thin group, n = 10; 1.3 mm PERMATAPE, Mitek Sports Medicine) fixation and (2) pullout repair using 2.5 mm suture tape (thick group, n = 10; 2.5 mm PERMATAPE, Mitek Sports Medicine) fixation. The single-loop stitch MS technique was utilised. The MST complex specimens were placed on a tensile tester. The structural properties of the MST complex (yield load, maximum load, liner stiffness, and elongation at failure) were identified.

Results

No significant differences were found between the thin and thick groups in terms of maximum load (108.8 ± 49.6 vs. 90.1 ± 33.6 N; p = 0.34), yield load (43.8 ± 15.2 vs. 39.4 ± 15.5 N; p = 0.53), liner stiffness (12.6 ± 8.4 vs. 11.2 ± 5.5 N/mm; p = 0.45), and elongation at failure (27.1 ± 19.4 vs. 19.9 ± 10.0 mm; p = 0.32).

Conclusion

The structural properties of the thickness of the different UHMWPE were comparable in MMPRT repair. Additionally, 1.3 mm PERMATAPE may demonstrate similar repair potential as 2.5 mm PERMATAPE.

Level of Evidence

Level Ⅳ.

Greater medial proximal tibial slope is associated with bone marrow lesions in middle-aged women with early knee osteoarthritis

BACKGROUND

Bone marrow lesion (BML) is an important magnetic resonance finding (MRI) finding that predicts knee osteoarthritis. The purpose of this study was to investigate the influence of proximal tibial morphology on BML, including the spreading root sign (SRS), in women without radiographic knee osteoarthritis (OA). It was hypothesized that varus alignment and a greater posterior tibial slopes (PTS) are associated with BML.

MATERIALS AND METHODS

A total of 359 female volunteers without knee OA who were participants in the Iwaki Health Promotion Project in 2017 or 2019 were enrolled. Participants were divided into the non-OA and early knee OA (EKOA) groups based on the Luyten's classification criteria. The presence of pathological cartilage lesions, BMLs, attritions, meniscal lesions and effusions was scored on T2-weighted fat-suppressed magnetic resonance imaging (MRI) according to the Whole-Organ MRI Scoring system. The medial proximal tibial angle (MPTA) and medial and lateral PTS (MPTS and LPTS, respectively) were measured. Regression and receiver operating characteristic (ROC) analyses were performed to reveal the relationship between BMLs and proximal tibial morphological parameters.

RESULTS

Of the 359 participants, 54 (15%) were classified as having EKOA. The prevalence of cartilage lesions, BMLs, attritions, meniscal lesions and effusions was higher in the EKOA group than in the non-OA group. The two groups had no significant difference in the proximal tibial parameters. Regression analysis revealed that age and a smaller MPTA were associated with BML in both groups. Attrition (p = 0.029) and the MPTS (p = 0.025) were positively associated with BML in the EKOA group.

CONCLUSION

The prevalence of BMLs was higher in women with EKOA and correlated with the varus and greater posterior slopes in those without radiographic knee OA.

LEVEL OF EVIDENCE

Level III, retrospective case-control study.

Editorial Commentary: Anatomic Morphologies of the Femur and Tibia and the Femorotibial Interactions Affect the Development of Medial Meniscus Posterior Root Tear

Medial meniscus posterior root tears (MMPRTs) occur frequently in middle-aged and older individuals. Female sex, increased body mass index, lower sports activity level, chondral lesions of the far posterior femoral condyles, anterior cruciate ligament degeneration, greater varus mechanical axis angle, steeper posterior slope of the medial tibial plateau, shallow concave shape of the medial tibial plateau, narrower intercondylar distance and notch width, bony spur formation, and medial meniscus posterior root impingement have been reported as significant risk factors for MMPRT development. Orthopaedic surgeons should recognize that the anatomic morphologies of the femur and tibia and the femorotibial interactions can affect the development of MMPRTs by increasing pathologic mechanical stresses on the medial meniscus posterior root.

Increased Medial Femoral Condyle Angle and Narrow Intercondylar Notch Are Associated With Medial Meniscus Posterior Root Tear

PURPOSE

To investigate the correlation between nontraumatic medial meniscus posterior root tear (MMPRT) and bone morphology of the knee with a particular emphasis on MMPR impingement.

METHODS

Magnetic resonance imaging (MRI) findings were examined between January 2018 and December 2020. MRI findings of patients with traumatic MMPRT, Kellgren Lawrence stage 3-4 arthropathy on radiographs, single- or multiple-ligament injuries and/or those who underwent treatment for these diseases, and surgery in and around the knee were excluded from the study. MRI measurements included medial femoral condylar angle (MFCA), intercondylar distance (ICD), and intercondylar notch width (ICNW), distal/posterior medial femoral condylar offset ratio, notch shape, medial tibial slope (MTS) angle, and medial proximal tibial angle (MPTA) measurements and spur presence and were compared between groups. All measurements were performed by two board-certified orthopedic surgeons on a best agreement basis.

RESULTS

MRI examinations of patients aged 40-60 were analyzed. MRI findings were divided into two groups: the study group of MRI findings of patients with MMPRT (n = 100) and the control group of MRI findings of patients without MMPRT (n = 100). MFCA was found to be significantly higher in the study group (mean: 46.5 ± 3.58) than in the control group (mean: 40.04 ± 4.61) (P < .001). In the study group, the ICD (study group mean: 76.26 ± 4.89; control group mean: 78.18 ± 6.1) was significantly narrower (P = .018), and the ICNW (study group mean: 17.19 ± 2.23; control group mean: 20.48 ± 2.13) was significantly shorter (P < .001). The ICNW/ICD ratio was significantly lower in patients in the study group (0.22 ± 0.02) than in the control group (0.25 ± 0.02) (P < .001). Bone spurs were present in 84% of the study group and only in 28% of those in the control group. In the study group, the most common notch type was A-type with 78%, while the least common was the U-type notch with 10%. However, in the control group, the most common notch type was A-type with 43%, and the least common was the W-type notch with 22%. The distal/posterior medial femoral condylar offset ratio was statistically lower in the study group (0.72 ± 0.07) than in the control group 0.78 ± 0.07) (P < .001). No significant intergroup differences were found in MTS (study group mean: 7.51 ±2.59; control group mean: 7.83 ± 2.57) (P = .390) and MPTA (study group mean: 86.92 ±2.15; control group mean: 87.48 ±1.8) measurements (P = .67).

CONCLUSIONS

Increased medial femoral condylar angle, low distal/posterior femoral offset ratio, narrow intercondylar distance and intercondylar notch width, A-type notch shape, and spur presence are associated with MMPRT.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

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.

The clinical and radiographic outcomes of type 2 medial meniscus posterior root tears following transtibial pullout repair

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.

Simultaneous Correction of Varus Deformity and Posterior Tibial Slope by Modified Hybrid Closed-Wedge High Tibial Osteotomy

A large posterior tibial slope has been proven to be a risk factor for anterior cruciate ligament (ACL) injuries, ACL graft failure, and medial meniscus posterior root tear. In addition, such pathologies often are accompanied by varus alignment. Thus, simultaneous varus and slope-correction osteotomy is required in such cases. High tibial osteotomy (HTO) is a well-established treatment for medial compartment knee osteoarthritis. Several HTO surgical techniques have been proposed, and hybrid closed-wedge HTO has been found to correct both varus deformity and a large posterior tibial slope via modification of the transverse osteotomy procedure. This Technical Note describes a modified hybrid closed-wedge HTO for simultaneous varus and slope correction in patients with ACL deficiency and/or medial meniscus posterior root tear involving both varus deformity and a large posterior tibial slope. This technique may reduce the risk of failure of the ACL graft and/or repaired medial meniscus posterior root.

Clinical outcomes of medial meniscus posterior root repair: A midterm follow-up study

BACKGROUND

Transtibial pullout repair of medial meniscus posterior root tears (MMPRTs) cannot prevent the progression of knee osteoarthritis. Conversions of knee arthroplasties are occasionally required following MMPRT repair. However, other knee-related surgical treatments following MMPRT repair are unclear. This study was aimed at investigating the midterm clinical outcomes and knee-related surgical events following MMPRT repair.

METHODS

Patients with MMPRT underwent pullout repair using FasT-Fix modified Mason-Allen (F-MMA) suturing with an all-inside meniscal repair device. Thirty-two patients with follow-up duration >2 years were enrolled. We assessed the clinical outcomes and postoperative surgical treatment of both knees.

RESULTS

F-MMA pullout repair improved all clinical evaluation scores in patients with MMPRT at a mean follow-up of 36.1 months. Postoperative arthroscopic debridement was required for one patient. An additional MMPRT repair was performed in one patient on second-look arthroscopy. None of the patients required ipsilateral knee arthroplasty. In the contralateral knees, one pullout repair of a newly developed MMPRT and two knee arthroplasties were performed.

CONCLUSIONS

This study demonstrated that F-MMA pullout repair yielded satisfactory clinical outcomes. However, subsequent knee-related surgeries were observed in 6.3% of the pullout-repaired knees and 9.4% of the contralateral knees. Our results suggest that surgeons should be aware of the worsening and/or occurrence of contralateral knee joint disease, even when the postoperative clinical outcomes are satisfactory following MMPRT repair.

LEVEL OF EVIDENCE

IV.

Internal tibial torsion is associated with medial meniscus posterior horn tears

PURPOSE

Risk factors for meniscal tears play a decisive role in deciding on treatment and rehabilitation. The purpose of this study was to investigate the effect of tibial rotation on medial meniscus posterior horn tears (MMPHTs).

METHODS

This study is a retrospective case-control study. Fifty patients with meniscal tears and 57 knees with intact meniscus were compared. Tibial rotation, femoral version, tibial slope and knee varus were measured in each participant. Knee osteoarthritis was classified according to the Kellgren-Lawrence classification. Demographic characteristics were noted.

RESULTS

There were significant differences in the mean tibial torsion angles and mean mechanical axes between the groups. The mean tibial rotation and mean mechanical axis were 26.3° ± 6.7 and 3.7° ± 2.7 in the MMPHT group and 30.3° ± 8.4 and 2.05° ± 2.7 in the control group, respectively (p = 0.008, p = 0.002).

CONCLUSION

The current retrospective study has shown that tibial rotation is markedly reduced in patients with MMPHTs. Although the actual mechanism is not clear, the internal torsion of the tibia causes a decrease in the foot progression angle and increases the knee adduction moment, which in turn increases the medial tibial contact pressure. Internal torsion of the tibia, such as knee varus, may play a role in the aetiology of MMPHTs by this way. Whilst there was a significant difference in the mean varus and tibial torsion between the groups, there was no significant difference in the mean femoral version or tibial slope.

LEVEL OF EVIDENCE

III.

MRI study of medial meniscus degeneration of osteoarthritic knees with or without posterior root tear

Purpose

The purpose of this study was to compare the medial meniscus (MM) degeneration, meniscus extrusion, and tibial joint inclination by using MRI to consider the pathogenesis of posterior root tear (PRT) in medial-type knee osteoarthritis (KOA) both with and without medial meniscus posterior root tear (MMPRT).

Methods

This study used open MRI with flexion sagittal view and included 324 medial-type osteoarthritic knees with a Kellegren–Lawrence grade of 2 or less. Following the exclusion process, 151 knees were selected for MRI analysis. MM degeneration grading was performed according to Jerosch by 5 degrees of 0–4 in four different portions from anterior to posterior. MM medial extrusion (MMME), MM posterior extrusion (MMPE), medial tibial medial slope (MTMS), and medial tibial posterior slope (MTPS) were measured according to previous studies.

Results

MM degeneration in the anterior portion to MCL averaged 1.72 ± 0.67 in the PRT group (n = 48) and 1.40 ± 0.78 in the non-PRT group (n = 103). The degeneration grade was statistically higher in the PRT group than in the non-PRT group (p = 0.050). There was no difference in MM degeneration in the other three portions. MMME averaged 4.02 ± 1.12 mm in the PRT group and 3.11 ± 1.11 mm in the non-PRT group. MMPE averaged 4.22 ± 0.87 mm in the PRT group and 2.83 ± 1.12 mm in the non-PRT group. Both MMME and MMPE in the PRT group were statistically larger than those in the non-PRT group (p < 0.001). There was no difference in MTMS between the two groups. MTPS averaged 6.34 ± 2.25° in the PRT group and 5.28 ± 2.23° in the non-PRT group. The MTPS of the PRT group was statistically larger than that of the non-PRT group (p = 0.007).

Conclusion

The severity of MM degeneration, extrusion of MM, and degree of tibial slope were compared between medial-type KOA with and without PRT using an open MRI. MM degeneration was more severe anteriorly in the PRT group. The PRT group showed larger MMME and MMPE with greater MTPS.

Level of evidence

III. Retrospective cohort study.

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.

[Posterior meniscus root tears]

Meniscus root tears are radial tears in the region of the posterior insertion zones. Medial root injuries usually occur in individuals > 50 years of age without adequate trauma and are associated with obesity and varus deformities. The root lesion leads to a loss of ring tension, which results in extrusion of the meniscus and a strong increase in joint pressure that is biomechanically equivalent to a complete meniscectomy. When indicating arthroscopic transosseous refixation of the medial root lesion, factors such as accompanying cartilage damage, osteoarthritis, obesity and varus deformity must be taken into account. Injuries to the root of the lateral meniscus are mostly observed in younger patients in combination with a rupture of the anterior cruciate ligament. Arthroscopic transosseous refixation in combination with cruciate ligament surgery is therefore also recommended for type I and type II lesions. In summary, both the medial and the lateral root lesions of the menisci are injuries with high biomechanical relevance.

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

Background

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

Methods

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

Results

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

Conclusions

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

Postoperative clinical outcomes of unicompartmental knee arthroplasty in patients with isolated medial compartmental osteoarthritis following medial meniscus posterior root tear

Background

Cartilage degradation progresses rapidly following medial meniscus posterior root tear (MMPRT). Unicompartmental knee arthroplasty (UKA) has been performed for medial compartmental osteoarthritis following MMPRT. We evaluated the clinical and radiographic outcomes of UKA for medial compartmental osteoarthritis after an untreated MMPRT.

Methods

Twenty-one patients who underwent UKA for isolated medial compartment osteoarthritis following MMPRT were retrospectively investigated. Clinical outcomes were assessed using the Knee Injury and Osteoarthritis Outcome Score and knee range of motion. The posterior tibial slope and tibial component inclination were evaluated using plain radiographs.

Results

The mean follow-up periods were 25.5 ± 13.8 months. Clinical outcomes improved significantly postoperatively. The mean postoperative knee extension angle was −1.1° ± 2.1°, and the knee flexion angle was 134.3° ± 4.9°. The posterior tibial slope angle decreased from 9.0° ± 2.0° preoperatively to 5.4° ± 1.8° postoperatively, and postoperative tibial component inclination at the final follow-up was 2.9° ± 1.1° varus. No aseptic loosening or deep infections were observed.

Conclusion

UKA significantly improved clinical outcomes and could be a viable surgical option for treating isolated medial compartmental osteoarthritis accompanied by untreated MMPRT.

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.