Preoperative sizing of meniscal allografts in meniscus transplantation

Current advances in engineering meniscal tissues: insights into 3D printing, injectable hydrogels and physical stimulation based strategies

The knee meniscus is the cushioning fibro-cartilage tissue present in between the femoral condyles and tibial plateau of the knee joint. It is largely avascular in nature and suffers from a wide range of tears and injuries caused by accidents, trauma, active lifestyle of the populace and old age of individuals. Healing of the meniscus is especially difficult due to its avascularity and hence requires invasive arthroscopic approaches such as surgical resection, suturing or implantation. Though various tissue engineering approaches are proposed for the treatment of meniscus tears, three-dimensional (3D) printing/bioprinting, injectable hydrogels and physical stimulation involving modalities are gaining forefront in the past decade. A plethora of new printing approaches such as direct light photopolymerization and volumetric printing, injectable biomaterials loaded with growth factors and physical stimulation such as low-intensity ultrasound approaches are being added to the treatment portfolio along with the contemporary tear mitigation measures. This review discusses on the necessary design considerations, approaches for 3D modeling and design practices for meniscal tear treatments within the scope of tissue engineering and regeneration. Also, the suitable materials, cell sources, growth factors, fixation and lubrication strategies, mechanical stimulation approaches, 3D printing strategies and injectable hydrogels for meniscal tear management have been elaborated. We have also summarized potential technologies and the potential framework that could be the herald of the future of meniscus tissue engineering and repair approaches.

Unique Anatomical Features of the Discoid Lateral Meniscus via Three-Dimensional MRI

Background The discoid lateral meniscus (DLM) is a unique anatomical variant characterized by a larger, thicker lateral meniscus. For clinical diagnosis of DLM, coronal and sagittal slices in two-dimensional (2D) MRI and arthroscopic imaging are typically employed. However, evaluating the entire shape of the DLM is challenging due to the limited views and details provided by these methods. Three-dimensional (3D) visualization with MRI offers a more comprehensive view of the entire meniscus. The purpose of this study was to demonstrate the entire shape of a DLM using 3D images and unveil its unique characteristics. Methods The study population consisted of 31 knees diagnosed with DLM through arthroscopic examination at our hospital between 2017 and 2021. This group comprised 20 males (65%) and 11 females (35%), with ages ranging from 9 to 49 years (mean age, 24.2 years). Furthermore, a control group of 43 knees without DLM was included for comparative analysis. This control group consisted of 22 males (51%) and 21 females (49%), with ages ranging from 9 to 69 years (mean age, 28.5 years). 3D images of the medial meniscus (MM) and lateral meniscus (LM) were reconstructed from 1.5T-MRI images with semi-automatic segmentation using free software. From the coordinate information, the anterior-to-posterior lengths of the MM and LM were obtained, and the medial-to-lateral anterior-to-posterior length (L/M ratio) ratio was calculated and compared with the value of the non-DLM population. Results Our method allows for the detailed delineation of the DLM's unique morphology. The DLM group exhibited a significantly smaller L/M ratio compared to the non-DLM group (DLM: 0.66±0.06, non-DLM: 0.74±0.05, p<0.001). Conclusions Reconstructed 3D images could help to demonstrate the whole morphology of DLM and reveal its unique features, in which DLM shows a significantly smaller L/M ratio as compared to non-DLM.

Meniscus Size Differs Between Patient and Donor Populations for Meniscus Allograft Transplantation

Purpose

To determine the extent of variability in meniscus size and anthropometric data between donors (supply) and patients (demand), to evaluate potential factors that may contribute to size discrepancies, and to determine whether the discrepancies lead to longer patient wait times.

Methods

Lateral and medial meniscal measurements, anthropometric data, and time to match a donor graft were extracted from a tissue supplier database. The frequency and distribution of meniscus size were analyzed. Body mass index (BMI), relative meniscus area, body mass to meniscus area index, and height to meniscus area index were compared between patient and donor pools via χ² tests and independent samples t-test. The effect of size on time to match was analyzed using analysis of variance and post-hoc Tukey test.

Results

The lateral meniscus patient population showed a greater frequency of larger size requirements compared to the donor population (P < .001) and the medial meniscus patient population showed a higher frequency of smaller meniscus size requirements (P < .001). The medial meniscus analysis showed significantly smaller meniscus areas (P < .001) in the patient population contributing to the observed trend of an increased body mass to meniscus area index and height to meniscus area index. The time to match a donor meniscus was affected by the patient meniscus size.

Conclusions

This analysis demonstrates variations in frequency of meniscus sizes between donor and patient populations. This variation is attributed to differences in anthropometric data between patient and donor populations. This work identifies a mismatch between demand and supply for certain patient sizes contributing to longer times to match.

Clinical Relevance

This work associated donor and patient mismatches with longer wait times. This can be useful for patient counseling as well as provide a framework to determine whether there are solutions within the current meniscus donor pool that can be used to meet this clinical need.

Identification of the joint line in revision total knee arthroplasty using a multiple linear regression model: a cadaveric study

INTRODUCTION

The results of revision total knee arthroplasty (rTKA) may be compromised by excessive joint line (JL) elevation. It is critical but challenging in reestablishing the JL in rTKA. Previous studies have confirmed that, biomechanically and clinically, JL elevation should not exceed 4 mm. Image-based studies described several approaches to locate the JL intraoperatively, however magnification errors could occur. In this cadaveric study, we aim to define an accurate and reliable method to determine the JL.

MATERIALS AND METHODS

Thirteen male and eleven female cadavers were used, with an average age of death being 48.3 years. The transepicondylar width (TEW), the distance from the medial (MEJL) and lateral (LEJL) epicondyle, adductor tubercle (ATJL), fibular head (FHJL) and tibial tubercle (TTJL) to the JL were measured in 48 knees. Intra- and interobserver reliability and validity were tested prior to any additional analysis. Pearson correlation and linear regression analysis were used to examine the correlations between landmark-JL distances (LEJL, MEJL, ATJL, FHJL and TTJL) and the TEW, and to further derive models for intraoperative JL determination. The accuracy of different models, quantified by errors between estimated and measured landmark-JL distances, was compared using the Friedman and post hoc Dunn tests.

RESULTS

The intra- and inter-observer measurements for TEW, MEJL, LEJL, ATJL, TTJL and FHJL did not differ significantly (p > 0.05). Between genders, significant differences were found on TEW, MEJL, LEJL, ATJL, FHJL and TTJL (p < 0.05). There was no association between TEW and either FHJL or TTJL (p > 0.05), while ATJL, MEJL, and LEJL were found to be correlated with TEW (p < 0.05). Six models were derived: (1) MEJL = 0.37*TEW (r = 0.384), (2) LEJL = 0.28*TEW (r = 0.380), (3) ATJL = 0.47*TEW (r = 0.608), (4) MEJL = 0.413*TEW - 4.197 (R² = 0.473), (5) LEJL = 0.236*TEW + 3.373 (R² = 0.326), (6) ATJL = 0.455*TEW + 1.440 (R² = 0.556). Errors were defined as deviations between estimated and actual landmark-JL distances. The mean absolute value of the errors, created by Model 1-6 was 3.18 ± 2.25, 2.53 ± 2.15, 2.64 ± 2.2, 1.85 ± 1.61, 1.60 ± 1.59 and 1.71 ± 1.5, respectively. The error could be limited to 4 mm in 72.9%, 83.3%, 72.9%, 87.5%, 87.5%, and 93.8% of the cases by referencing Model 1-6, respectively.

CONCLUSION

Compared to previous image-based measurements, the current cadaveric study most closely resembles a realistic view of intraoperative settings and could circumvents magnification errors. We recommend using Model 6, the JL can be best estimated by referencing the AT and the ATJL can be calculated as ATJL (mm) = 0.455*TEW (mm) + 1.440 (mm).

Autologous semitendinosus meniscus graft significantly improves knee joint kinematics and the tibiofemoral contact after complete lateral meniscectomy

PURPOSE

The purpose of this study was to investigate the potential of a doubled semitendinosus (ST) and a single gracilis tendon (GT) lateral meniscus autograft to restore the knee joint kinematics and tibiofemoral contact after total lateral meniscectomy (LMM).

METHODS

Fourteen human knee joints were tested intact, after LMM and after ST and GT meniscus autograft treatment under an axial load of 200 N during full range of motion (0°-120°) and four randomised loading situations: without external moments, external rotation, valgus stress and a combination of external rotation and valgus stress using a knee joint simulator. Non-parametric statistical analyses were performed on joint kinematics and on the tibiofemoral contact mechanics.

RESULTS

LMM led to significant rotational instability of the knee joints (p < 0.02), which was significantly improved after ST autograft application (p < 0.04), except for knee joint flexions > 60°. The GT autograft failed to restore the joint kinematics. LMM significantly increased the tibiofemoral contact pressure (p < 0.03), while decreasing the contact area (p < 0.05). The ST autograft was able to restore the contact mechanics after LMM (p < 0.02), while the GT replacement displayed only an improvement trend.

CONCLUSION

The doubled ST lateral meniscus autograft improved the knee joint kinematics significantly and restored the tibiofemoral contact mechanics almost comparable to the native situation. Thus, from a biomechanical point of view, ST meniscus autografts might be a potential treatment alternative for patients who are indicated for meniscus allograft transplantation.

High-grade preoperative osteoarthritis of the index compartment is a major predictor of meniscal allograft failure

INTRODUCTION

Preoperatively available predictors of meniscal allograft failure would help in patient counseling and surgical indication for meniscal allograft transplantation (MAT). It was hypothesized that young patient age, high posterior tibial slope (PTS), and high-grade osteoarthritis (OA) are predictors of meniscal allograft failure.

MATERIALS AND METHODS

Patients undergoing MAT with a minimum follow-up of 2 years were included in this retrospective study. Demographic and surgical data, and causes of meniscal allograft failure were collected. PTS and degree of OA (low-grade: Kellgren-Lawrence 0, 1, and 2; high-grade: Kellgren-Lawrence 3 and 4) of the index and opposite tibiofemoral compartments were determined on preoperative radiographs.

RESULTS

This study included 77 patients with a mean age of 25.7 ± 10.1 years at the time of MAT. After a mean follow-up of 7.6 ± 5.6 years, meniscal allograft failure was observed in 26 patients (34%). The median time from MAT to meniscal allograft failure was 1.3 years (inter-quartile range, 2.5 years). Meniscal allograft tears (88%) were the primary cause of graft failure, followed by high-grade OA (12%). Patients experiencing meniscal allograft failure were an average of 2.7 years (95% CI [2.2, 7.5], p = 0.202) older at the time of MAT than patients without failure. PTS was not found to be a predictor of meniscal allograft failure (odds ratio, 0.884 (95% CI [0.727, 1.073], p = 0.212)). Patients with high-grade preoperative OA of the index compartment had 28 times higher odds of experiencing meniscal allograft failure than patients with low-grade preoperative OA (p = 0.008).

CONCLUSIONS

High-grade preoperative OA of the index compartment was found to be a significant and clinically relevant predictor of meniscal allograft failure. Surgeons should be aware of the impact of OA on meniscal allograft survival, which needs to be considered in patient counseling and surgical indication for MAT in patients.

Variations of cross-sectional meniscal morphology between similar-sized menisci: implications on donor selection for meniscal allograft transplantation

PURPOSE

This study aimed to investigate the morphological variations in the cross-sectional anatomy of the meniscus between similar-sized matched menisci.

MATERIALS AND METHODS

Knee MRI of 329 patients with intact menisci were retrospectively reviewed, and the meniscal length (ML), meniscal width (MW), and cross-sectional dimensions (meniscal height and width) of the anterior, posterior horns, and the corpus were measured. Patients with similar-sized menisci who had less than 1 mm difference in ML and MW were matched. 330 male-to-male medial menisci (MM), 623 male-to-male lateral menisci (LM), 82 female-to-female MM, 233 female-to-female LM, 176 cross-gender MM, and 265 cross-gender LM unique combination of ideally matched pairs (total: 1709) were generated. The disparity in the cross-sectional dimensions, absolute difference, and the paired percent differences was statistically analyzed.

RESULTS

The ML and MW in all groups were statistically similar, with a predefined absolute difference of 1 mm both for ML and MW (paired percent difference < 5%). The cross-sectional segmental meniscal dimensions were similar within all groups, but the paired percent differences showed high variations between a mean of 12.1-21.5% and up to 150.9%. The paired percent difference of MM in each segmental dimension was similar among different gender combinations. However, segmental paired percent differences of LM showed statistical differences in anterior horn width (AHW) (p: 0.001) and posterior horn width (PHW) (p: 0.001). In subgroup comparisons, the paired percent difference of AHW was higher in the female-to-female group compared to cross-gender (p: 0.023) and male-to-male groups (p: 0.001). The paired percent difference of PHW was smaller in the male-to-male group compared to female-to-female and cross-gender groups (p: 0.001 for both).

CONCLUSIONS

Segmental cross-sectional anatomy showed wide variations despite strict matching in ML and MW. These variations were present in all gender combinations. The meniscal 3D shape is unique, but acceptable limits of similarity need further research.

LEVEL OF EVIDENCE

Retrospective study, Level III.

Post-Traumatic Osteoarthritis Assessment in Emerging and Advanced Pre-Clinical Meniscus Repair Strategies: A Review

Surgical repair of meniscus injury is intended to help alleviate pain, prevent further exacerbation of the injury, restore normal knee function, and inhibit the accelerated development of post-traumatic osteoarthritis (PTOA). Meniscus injuries that are treated poorly or left untreated are reported to significantly increase the risk of PTOA in patients. Current surgical approaches for the treatment of meniscus injuries do not eliminate the risk of accelerated PTOA development. Through recent efforts by scientists to develop innovative and more effective meniscus repair strategies, the use of biologics, allografts, and scaffolds have come into the forefront in pre-clinical investigations. However, gauging the extent to which these (and other) approaches inhibit the development of PTOA in the knee joint is often overlooked, yet an important consideration for determining the overall efficacy of potential treatments. In this review, we catalog recent advancements in pre-clinical therapies for meniscus injuries and discuss the assessment methodologies that are used for gauging the success of these treatments based on their effect on PTOA severity. Methodologies include histopathological evaluation of cartilage, radiographic evaluation of the knee, analysis of knee function, and quantification of OA predictive biomarkers. Lastly, we analyze the prevalence of these methodologies using a systemic PubMed® search for original scientific journal articles published in the last 3-years. We indexed 37 meniscus repair/replacement studies conducted in live animal models. Overall, our findings show that approximately 75% of these studies have performed at least one assessment for PTOA following meniscus injury repair. Out of this, 84% studies have reported an improvement in PTOA resulting from treatment.

Arthroscopic Centralization for Lateral Meniscal Injuries Reduces Laxity in the Anterior Cruciate Ligament-Reconstructed Knee

BACKGROUND

A lateral meniscal (LM) disorder is one factor that causes rotational laxity after anterior cruciate ligament (ACL) reconstruction (ACLR). There are different types of irreparable meniscal disorders, one of which is a massive meniscal defect.

HYPOTHESIS/PURPOSE

The purpose of this study was to evaluate the kinematic effects of arthroscopic centralization on an irreparable LM defect. The hypothesis was that arthroscopic centralization for an irreparable LM defect with concomitant ACLR would improve knee rotational stability.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 14 fresh-frozen human cadaveric knees were tested in 4 states: (1) intact ACL and intact lateral meniscus, (2) reconstructed ACL and intact lateral meniscus, (3) reconstructed ACL and lateral meniscus defect, and (4) reconstructed ACL and centralized lateral meniscus. Anatomic ACLR was performed using an 8 mm-diameter hamstring tendon graft. An LM defect (20% of the anteroposterior length) was created arthroscopically, and arthroscopic centralization was performed. Kinematics were analyzed using a 6 degrees of freedom robotic system under 4 knee loads: (1) an 89.0-N anterior tibial load, (2) a 5.0-N·m external rotation tibial torque, (3) a 5.0-N·m internal rotation tibial torque, and (4) a simulated pivot-shift load with a combined 7.0-N·m valgus and 5.0-N·m internal rotation tibial torque.

RESULTS

LM centralization reduced anterior tibial translation similar to that of the ACLR intact LM state under anterior tibial loading (~2 mm at 30° of flexion) and showed 40% to 100% of tibial displacement in the 4 knee states under simulated pivot-shift loading. The procedure overconstrained the knee under internal rotation tibial torque and simulated pivot-shift loading.

CONCLUSION

Arthroscopic centralization reduced knee laxity after ACLR for a massive LM defect in a cadaveric model.

CLINICAL RELEVANCE

In cases involving irreparable LM injuries during ACLR, consideration should be given to arthroscopic centralization for reducing knee laxity. However, the procedure may overconstrain the knee in certain motions.

Association Between Meniscal Allograft Tears and Early Surgical Meniscal Allograft Failure

BACKGROUND

Meniscal allograft transplantation (MAT) has become a viable treatment option for patients with symptomatic meniscal deficiency. Some patients experience early surgical meniscal allograft failure attributed to causes that have not yet been sufficiently clarified.

PURPOSE

To evaluate the prevalence, types, and distribution of arthroscopically confirmed meniscal allograft tears and the associated effect on surgical meniscal allograft survival.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients undergoing MAT with a minimum 2-year follow-up were retrospectively reviewed. Descriptive and surgical data were collected. Type and location of arthroscopically confirmed meniscal allograft tears were recorded and compared between medial and lateral allografts and suture-only and bone block fixation. A survival analysis was conducted to evaluate the effect of meniscal allograft tears on surgical meniscal allograft survival.

RESULTS

This study included 142 patients (54% male; mean ± SD age, 29.6 ± 10.4 years) with a mean follow-up of 10.3 ± 7.5 years. The prevalence of meniscal allograft tears was 32%, observed at a median of 1.2 years (interquartile range, 2.8 years) after MAT. The posterior horns were most frequently affected, followed by the posterior roots, midbodies, anterior horns, and anterior roots. The most frequently observed tear types were root tears (43%), followed by longitudinal, horizontal, radial, complex, bucket-handle, and meniscocapsular separation tears. A statistically significant association was found between meniscal allograft tear types and fixation techniques (P = .027), with root tears predominant after suture-only as compared with bone block fixation (57% vs 22%). Patients with meniscal allograft root tears were a mean of 5.4 years (95% CI, 1.6-9.2 years; P = .007) younger than were patients without root tears. The 1-year surgical meniscal allograft survival rate was significantly lower for torn versus intact meniscal allografts (75% vs 99%; P < .001).

CONCLUSION

Meniscal allograft root tears were predominant, associated with younger patient age, and more often observed when using the suture-only fixation technique versus the bone block fixation technique. Torn meniscal allografts were associated with early surgical graft failure when compared with intact meniscal allografts, resulting in a significantly lower 1-year survival rate.

Radiographic Methods Are as Accurate as Magnetic Resonance Imaging for Graft Sizing Before Lateral Meniscal Transplantation

BACKGROUND

Accurate allograft matching is deemed critical for meniscal transplantation; thus, precise measurements are essential to correctly calculate meniscal size. Several methods for meniscal sizing have been described, but there remains a discussion on which is the most accurate for the lateral meniscus.

PURPOSE

To compare the accuracy of radiographic, anthropometric, and magnetic resonance imaging (MRI) methods of determining width and length of the lateral meniscus with actual dimensions after anatomic dissection.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen human cadaveric knees without any evidence of meniscal or ligamentous injury were primarily imaged using radiography and MRI and subsequently underwent dissection to assess the anatomic size of each meniscus. Four methods were used to predict the size of the lateral menisci: anthropometric, radiographic (Pollard and Yoon), and MRI. Absolute differences in length and width between actual and predicted sizes were determined.

RESULTS

The anatomic lateral meniscal width and length were 33.01 ± 4.25 mm (mean ± SD; range, 24.84-40.18 mm) and 31.41 ± 5.06 mm (range, 25.2-40.05 mm), respectively. Regarding width, the anthropometric method demonstrated an absolute difference from anatomic measurement significantly greater when compared with the Pollard technique and MRI (P = .002). Regarding length, the Pollard method presented an absolute difference significantly greater than all other techniques (P = .003). In terms of the ability to measure width and length, MRI accurately predicted meniscal size within 10% of the anatomic size in 65% of measurements, the Yoon method in 54%, and the Pollard method in 20% (P = .01). Radiographs tended to overestimate the true size of the lateral meniscus, while the anthropometric technique overestimated width in all specimens.

CONCLUSION

This study demonstrated that MRI and the Yoon radiographic method are comparable in terms of accuracy for graft sizing before lateral meniscal transplantation. While MRI is useful, a contralateral MRI is required, which makes the Yoon radiographic method recommended given the ease and cost advantage. The original Pollard technique and the anthropometric method are not recommended.

CLINICAL RELEVANCE

Over- and undersizing of meniscal transplants has been implicated in graft failure. Therefore, increasing the reliability of preoperative meniscal measurements is deemed important for the success of meniscal allograft transplantation.

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.

Meniscus sizing using three-dimensional models of the ipsilateral tibia plateau based on CT scans - an experimental study of a new sizing approach

Purpose

Selection of a meniscus allograft with a similar three-dimensional (3D) size is essential for good clinical results in meniscus allograft surgery. Direct meniscus sizing by MRI scan is not possible in total meniscectomy and indirect sizing by conventional radiography is often inaccurate. The purpose of this study was to develop a new indirect sizing method, based on the 3D shape of the ipsilateral tibia plateau, which is independent of the meniscus condition.

Methods

MRI and CT scans of fifty healthy knee joints were used to create 3D surface models of both menisci (MRI) and tibia plateau (CT). 3D bone models of the proximal 10 mm of the entire and half tibia plateau (with / without intercondylar area) were created in a standardized fashion. For each meniscus, the best fitting “allograft” couple out of all other 49 menisci were assessed by the surface distance of the 3D meniscus (best available allograft), of the 3D tibia plateau (3D-CT) and by the radiographic method of Pollard (2D-RX).

Results

3D-CT sizing was significantly better by using only the half tibia plateau without the intercondylar area (p < 0.001). But neither sizing by 3D-CT, nor by 2D-RX could select the best available allograft. Compared to 2D-RX, 3D-CT sizing was significantly better for the medial, but not for the lateral meniscus.

Conclusions

Automatized, indirect meniscus sizing using the 3D bone models of the tibia plateau is feasible and more precise than the previously described 2D-RX method.. However, further technical improvement is needed to select always the best available allograft.

Three-dimensional meniscus allograft sizing-a study of 280 healthy menisci

Background

Inaccurate meniscus allograft size is still an important problem of the currently used sizing methods. The purpose of this study was to evaluate a new three-dimensional (3D) meniscus-sizing method to increase the accuracy of the selected allografts.

Methods

3D triangular surface models were generated from 280 menisci based on 50 bilateral and 40 unilateral knee joint magnetic resonance imaging (MRI) scans. These models served as an imaginary meniscus allograft tissue bank. Meniscus sizing and allograft selection was simulated for all 50 bilateral knee joints by (1) the closest mean surface distance (MeSD) (3D-MRI sizing with contralateral meniscus), (2) the smallest meniscal width/length difference in MRI (2D-MRI sizing with contralateral meniscus), and (3) conventional radiography as proposed by Pollard (2D-radiograph (RX) sizing with ipsilateral tibia plateau). 3D shape and meniscal width, length, and height were compared between the original meniscus and the selected meniscus using the three sizing methods.

Results

Allograft selection by MeSD (3D MRI) was superior for all measurement parameters. In particular, the 3D shape was significantly improved (p < 0.001), while the mean differences in meniscal width, length, and height were only slightly better than the allograft selected by the other methods. Outliers were reduced by up to 55% (vs. 2D MRI) and 83% (vs. 2D RX) for the medial meniscus and 39% (vs. 2D MRI) and 56% (vs. 2D RX) for the lateral meniscus.

Conclusion

3D-MRI sizing by MeSD using the contralateral meniscus as a reconstruction template can significantly improve meniscus allograft selection. Sizing using conventional radiography should probably not be recommended.

Trial registration

Kantonale Ethikkommission Zürich had given the approval for the study (BASEC-No. 2018-00856).

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

Introduction

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

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

Methods

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

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

Results

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

Conclusion

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

Arthroscopic centralization restores residual knee laxity in ACL-reconstructed knee with a lateral meniscus defect

PURPOSE

The aim of this study was to evaluate the effects of knee biomechanics with an irreparable lateral meniscus defect using the centralization capsular meniscus support procedure in the setting of the ACL-reconstructed knee in a porcine model. The hypothesis is the arthroscopic centralization will decrease the laxity and rotation of the ACL-reconstructed knee.

METHODS

Twelve fresh-frozen porcine knees were tested using a robotic testing system under the following loading conditions: (a) an 89.0 N anterior tibial load; (b) 4.0 N m internal and external rotational torques. Anatomic single-bundle ACL reconstruction with a 7 mm-diameter bovine extensor tendon graft was performed. A massive, middle segment, lateral meniscus defect was created via arthroscopy, and arthroscopic centralization was performed with a 1.4 mm anchor with a #2 suture. The LM states with ACL reconstruction evaluated were: intact, massive middle segment defect and with the lateral meniscus centralization procedure.

RESULTS

The rotation of the ACL reconstructed knee with the lateral meniscus defect was significantly higher than with the centralized lateral meniscus under an external rotational torque at 30° of knee flexion, and under an internal rotational torque at 30° and 45° of knee flexion. There were no systematic and consistent effects of LM centralization under anterior tibial translation.

CONCLUSIONS

In this porcine model, the capsular support of middle segment of the lateral meniscus using arthroscopic centralization improved the residual rotational laxity of the ACL-reconstructed knee accompanied with lateral meniscus dysfunction due to massive meniscus defect. This study quantifies the benefit to knee kinematics of arthroscopic centralization by restoring the lateral meniscal function.

Bone-Plug Versus Soft Tissue Fixation of Medial Meniscal Allograft Transplants: A Biomechanical Study

BACKGROUND

It is controversial whether soft tissue fixation only and bone-plug techniques for medial meniscal allograft transplantation provide equivalent fixation and restoration of load distribution. Prior studies on this topic did not re-create the clinical situation with use of size-, side-, and compartment-matched meniscal transplants.

HYPOTHESIS

Both techniques will provide equivalent fixation of the meniscal transplant and restore load distribution and contact pressures similar to those of the native knee.

STUDY DESIGN

Controlled laboratory study.

METHODS

Nine fresh-frozen human cadaveric knees underwent mean contact pressure, mean contact area, and peak contact pressure evaluation in 4 medial meniscal testing conditions (native, total meniscectomy, bone-plug fixation, and soft tissue fixation) at 3 flexion angles (0°, 30°, and 60°) using Tekscan sensors under a 700-N axial load.

RESULTS

Medial meniscectomy resulted in significantly decreased contact area and increased contact pressure compared with the native condition at all flexion angles (P < .0001). Compared with the native state, soft tissue fixation demonstrated significantly higher mean contact pressure and lower mean contact area at 0° and 30° of flexion (P < .05), while bone-plug fixation showed no significant difference. There was no significant difference in peak contact pressure between study conditions.

CONCLUSION

Total medial meniscectomy leads to significantly worsened load distribution within the knee. Medial meniscal allograft transplantation can restore load parameters close to those of the native condition. The bone-plug technique demonstrated improved tibiofemoral contact pressures compared with soft tissue fixation.

CLINICAL RELEVANCE

Medial meniscal allograft transplantation with bone-plug fixation is a viable option to restore biomechanics in patients with meniscal deficiency.

Anatomical feature of knee joint in Aachen minipig as a novel miniature pig line for experimental research in orthopaedics

BACKGROUND

The pig is a commonly used large animal model, since pigs share anatomical and physiological similarities with humans. In contrast to other experimental pig lines the Aachen minipig, as a robust novel minipig does not require housing with any barrier. To estimate transferability of results to human conditions, pig lines should be thoroughly characterized.

PURPOSE

Therefore, we analyzed the anatomical pecularities of the knee joint of the novel "Aachen minipig" line raised for experimental conditions.

METHODS

Eight knee joints of four adult Aachen minipigs were dissected measuring the dimensions of typical landmarks using a digital caliper. Hybrid pig and human knee joints served as controls. Cartilage of the Aachen minipig (trochlear groove, femoral condyles, menisci) were assessed histologically.

RESULTS

The Aachen minipig shared its knee joint anatomy with the hybrid pig. In comparison to humans, peculiarities of the pig were demonstrated in the Aachen minipig: the lateral meniscus and the lateral tibial joint surface were significantly longer than the medial counterparts. The fibular head was covered by fibrocartilage and completely integrated into the lateral lower joint surface. The cartilage at the joint areas usually used for cartilage repair studies was in average 0.66±0.04mm thick. The porcine anterior cruciate ligament (ACL) attached with two bundles at the anterior tibial plateau separated from each other by the lateral anterior meniscotibial ligament. Aachen minipig articular and meniscal cartilage presented the typical histoarchitecture.

CONCLUSIONS

The Aachen minipig reflects porcine anatomical peculiarities, which should be considered, especially for meniscus and ACL reconstruction.

The 50 Most-Cited Articles in Meniscal Allograft Transplantation Research: A Bibliometric Analysis

OBJECTIVE

To identify the 50 most-cited articles in meniscal allograft transplantation (MAT) research and analyze their characteristics.

DESIGN

In September 2017, the Scopus database was queried to identify the 50 most-cited articles in MAT research. Variables analyzed include number of citations, publication year, journal, institution, country of origin, article type, study design, and level of evidence. Citation density was calculated for each article. The correlation between citation density and publication year and the correlation between level of evidence and number of citations, citation density, and publication year were computed.

RESULTS

The 50 most-cited articles were published in 12 journals between 1986 and 2011. The number of citations ranged from 59 to 290 (109.3 ± 48.6). Citation density ranged from 2.7 to 17.6 citations per year (7.0 ± 3.3). There was a positive correlation between citation density and publication year ( r = +0.489, P < 0.001). Overall, 56% of the articles were clinical and 44% were basic science. Of the 28 clinical articles, 61% were level IV or V evidence. Level of evidence was not significantly correlated with number of citations ( r = -0.059, P = 0.766), citation density ( r = +0.030, P = 0.880), or publication year ( r = -0.0009, P = 0.996).

CONCLUSION

This analysis provides the orthopedic community with a readily accessible list of the classic citations in MAT research and provides insight into the historical development of this procedure. Although there was a moderate positive correlation between citation density and publication year, articles with stronger levels of evidence were not more frequently cited despite the increasing trend toward evidence-based practice.

Biomechanical characterization of a novel collagen-hyaluronan infused 3D-printed polymeric device for partial meniscus replacement

The menisci transmit load by increasing the contact area and decreasing peak contact stresses on the articular surfaces. Meniscal lesions are among the most common orthopedic injuries, and resulting meniscectomies are associated with adverse polycaprolactone contact mechanics changes and, ultimately, an increased likelihood of osteoarthritis. Meniscus scaffolds were fabricated by 3D-printing a network of circumferential and radial filaments of resorbable polymer (poly(desaminotyrosyl-tyrosine dodecyl ester dodecanoate)) and infused with collagen-hyaluronan. The scaffold demonstrated an instantaneous compressive modulus (1.66 ± 0.44 MPa) comparable to native meniscus (1.52 ± 0.59 MPa). The scaffold aggregate modulus (1.33 ± 0.51 MPa) was within 2% of the native value (1.31 ± 0.36 MPa). In tension, the scaffold displayed a comparable stiffness to native tissue (127.6-97.1 N/mm) and an ultimate load of 33% of the native value. Suture pull-out load of scaffolds (83.1 ± 10.0 N) was within 10% of native values (91.5 ± 15.4 N). Contact stress analysis demonstrated the scaffold reduced peak contact stress by 60-67% and increased contact area by 38%, relative to partial meniscectomy. This is the first meniscal scaffold to match both the axial compressive properties and the circumferential tensile stiffness of the native meniscus. The improvement of joint contact mechanics, relative to partial meniscectomy alone, motivates further investigation using a large animal model. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2457-2465, 2019.

Meniscal sizing before allograft: Comparison of three imaging techniques

BACKGROUND

Accuracy of meniscal sizing is an important issue before allograft transplantation. To date, there is no consensus on the best imaging method. The purpose of this study was to compare plain radiographs, magnetic resonance imaging (MRI) and computed tomography (CT) arthrography in the assessment of meniscal size. We hypothesized that MRI and CT arthrography had better correlations than plain radiographs.

METHODS

All patients operated on by meniscal allograft between January 2005 and May 2015 were screened. Among them, 32 patients had both preoperative radiographs, MRI and CT arthrography of the affected knee. The meniscal dimensions were evaluated, blindly and randomly, using three imaging methods. A correlation analysis between each technique was made. For radiographic methods, an additional comparison was made between original Pollard's method and the modified method (Yoon). Bone dimensions (tibial metaphysis) were also collected, using radiographs and MRI, in order to build new equations allowing determination of meniscal dimensions from those bone measurements.

RESULTS

The radiographic methods offered satisfying evaluations of the meniscal dimensions in the sagittal plane, without significant difference when compared with CT arthrography or MRI. In the frontal plane, the radiograph methods were less effective. With new equations, allowing determination of meniscal dimensions from tibial plateau dimensions, the mean correlation coefficient was 0.39 (0.14-0.71).

CONCLUSIONS

The correlation between radiographic methods and MRI depended on which parameter (frontal or sagittal) was measured. Thus, we proposed a new method for sizing of meniscus, easily measurable from bony landmarks, aiming to improve the accuracy of graft selection.

Meniscal Allograft Transplantation Made Simple: Bridge and Slot Technique

Over recent years, appreciation for the critical role of the meniscus in joint biomechanics has led to an emphasis on meniscal preservation. Meniscal allograft transplant (MAT) is a promising biological solution for the symptomatic young patient with a meniscus-deficient knee that has not developed advanced osteoarthritis. As surgical techniques are refined and outcomes continue to improve, it is vital to consider the utility of such procedures and offer a straightforward approach to MAT. This article and accompanying video provide a step-by-step tutorial on how to perform a MAT using the bridge and slot technique, its key pearls and pitfalls as well as the relevant advantages and disadvantages of MAT.

The nutrition of the human meniscus: A computational analysis investigating the effect of vascular recession on tissue homeostasis

The meniscus is essential to the functioning of the knee, offering load support, congruency, lubrication, and protection to the underlying cartilage. Meniscus degeneration affects ∼35% of the population, and potentially leads to knee osteoarthritis. The etiology of meniscal degeneration remains to be elucidated, although many factors have been considered. However, the role of nutritional supply to meniscus cells in the pathogenesis of meniscus degeneration has been so far overlooked. Nutrients are delivered to meniscal cells through the surrounding synovial fluid and the blood vessels present in the outer region of the meniscus. During maturation, vascularization progressively recedes up to the outer 10% of the tissue, leaving the majority avascular. It has been hypothesized that vascular recession might significantly reduce the nutrient supply to cells, thus contributing to meniscus degeneration. The objective of this study was to evaluate the effect of vascular recession on nutrient levels available to meniscus cells. This was done by developing a novel computational model for meniscus homeostasis based on mixture theory. It was found that transvascular transport of nutrients in the vascularized region of the meniscus contributes to more than 40% of the glucose content in the core of the tissue. However, vascular recession does not significantly alter nutrient levels in the meniscus, reducing at most 5% of the nutrient content in the central portion of the tissue. Therefore, our analysis suggests that reduced vascularity is not likely a primary initiating source in tissue degeneration. However, it does feasibly play a key role in inability for self-repair, as seen clinically.

Knee Menisci

The menisci of the knees are semicircular fibrocartilaginous structures consisting of a hydrophilic extracellular matrix containing a network of collagen fibers, glycoproteins, and proteoglycans maintained by a cellular component. The menisci are responsible for more than 50% of load transmission across the knee and increase joint congruity thereby also aiding in fluid film lubrication of the joint. In the United Kingdom, meniscal tears are the most common form of intra-articular knee injury and one of the commonest indications for orthopedic intervention. The management of these injuries is dependent on the location within the meniscus (relative to peripheral blood supply) and the pattern of tear. Removal of meniscus is known to place the knee at increased risk of osteoarthritis; therefore repair of meniscal tears is preferable. However, a significant proportion of tears are irreparable and can only be treated by partial or even complete meniscectomy. More recent studies have shown encouraging results with meniscal replacement in this situation, though further work is required in this area.

Prospective Clinical and Radiographic Outcomes After Concomitant Anterior Cruciate Ligament Reconstruction and Meniscal Allograft Transplantation at a Mean 5-Year Follow-up

BACKGROUND

Concomitant anterior cruciate ligament reconstruction and meniscal allograft transplantation (ACLR/MAT) has demonstrated short-term success in small, retrospective cohort studies. Patient- and disease-specific predictors of success after ACLR/MAT are largely unknown.

PURPOSE

To (1) prospectively evaluate the subjective and objective clinical and radiographic outcomes after ACLR/MAT and (2) conduct a subgroup analysis to identify patient- or disease-related factors that correlate with failure.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patient-reported outcomes (PROs) were prospectively collected on 40 patients undergoing concomitant ACLR/MAT. Nineteen athletes responded to return-to-sport data. Clinical data (physical examination including Lachman and pivot-shift testing and KT-1000 arthrometer testing) were obtained on 28 patients who returned for an evaluation, while 24 of those patients additionally had radiographic data (progression of Kellgren-Lawrence [KL] grade and joint-space narrowing) evaluated. Reoperations and failures were documented for all patients at their final follow-up.

RESULTS

The overall cohort of 40 patients had a mean age of 30.3 ± 9.6 years (range, 16.0-54.0 years) and a mean body mass index of 27.7 ± 4.2 kg/m². The mean follow-up time was 5.7 ± 3.2 years (range, 1.7-16.5 years). There were 33 (83%) medial meniscal transplants performed compared with 7 (17%) lateral meniscal transplants. Patients underwent a mean of 2.9 ± 1.9 prior surgical procedures. Nineteen patients underwent concomitant procedures, including, most commonly, 9 hardware removals and 9 osteochondral allografts. There were significant improvements in 11 of 14 PRO measures as well as a 50% return-to-sport rate. Knee stability significantly improved in 28 patients who returned for a physical examination, and KT-1000 arthrometer testing indicated no differences between the affected and unaffected sides at final follow-up (mean, 0.9 ± 1.5 mm [range, -2 to 4 mm] in comparison to contralateral knee at 30 lb of testing; mean, 0.9 ± 1.9 mm [range, -4 to 4 mm] in comparison to contralateral knee at maximum manual strength). Significant improvements were seen in patients with Lachman grade ≥2A at final follow-up (18% vs 97%, respectively; P < .01) and with pivot shift ≥1+ at final follow-up (36% vs 94%, respectively; P < .01) compared with preoperatively. For the 24 patients with radiographic data, no significant joint-space decrease was recorded in the medial compartment for medial MAT-treated patients or the lateral compartment for lateral MAT-treated patients. The mean KL grade increased from 0.7 ± 0.8 to 1.6 ± 0.9 at final follow-up ( P < .01). There were no major (0%) and 2 minor (5%) complications, which constituted early postoperative drainage treated successfully with oral antibiotics. While 35% of patients underwent reoperations, the majority of these were simple arthroscopic debridements and occurred after nearly 4 years from the index surgery. The overall survival rate at final follow-up was 80%. Failures occurred at a mean of 7.3 years, and those who converted to arthroplasty did so at a mean of 8.3 years from the time of index ACLR/MAT. Patients with failed grafts were more frequently associated with workers' compensation claims (38% vs 13%, respectively) and less frequently self-identified as athletes (13% vs 56%, respectively) compared with patients with intact grafts.

CONCLUSION

Concomitant ACLR/MAT can provide significant improvements in clinical outcomes and enhancement in objective knee stability and was associated with an insignificant degree of radiographic joint-space narrowing changes with a 5-year survivorship of more than 80% for those with data available. Athlete status may be a preoperative predictor of midterm survival.

High meniscal slope angle as a risk factor for meniscal allograft extrusion

A meniscal graft extrusion is still an unresolved problem that affects most patients after a meniscal transplantation. Despite the advances in surgical techniques, together with the improved methods for a meniscal allograft sizing, success is only observed in up to 75% of patients after they experience a meniscal allograft transplantation. Because a meniscal extrusion is associated with a cartilage deterioration and the progression of osteoarthritis there is a great interest in how to prevent this phenomenon. The crucial factor for the minimisation of a meniscal allograft extrusion is by perfectly matching the implant. Most methods for a meniscal allograft sizing only focus on assessing the length and the width of the meniscus. Even though there is some evidence that there is a relationship between the shape of the meniscus in a cross-sectional plane and the meniscal extrusion, any of the planning methods do not take this factor into consideration. Although there is a large variability of meniscus shapes in cross-section, we hypothesise that by taking the meniscal slope into account during surgical planning, as well as performing the correct adjustments of this particular parameter, we can diminish the risk of a meniscal allograft extrusion.

Various factors contribute to graft extrusion in lateral meniscus allograft transplantation

PURPOSE

Lateral meniscus allograft transplantation (LMAT) is a feasible surgical option for young meniscus-deficient patients. Although several studies have explored the factors that contribute to graft extrusion, they have not been fully elucidated. The aim of this study was to determine the various factors that contribute to graft extrusion.

METHODS

Patients with knees that had received LMAT using a keyhole technique (n = 87 knees in 82 patients) were reviewed. The median age of these patients was 22 years (range 19-54 years), and the median postprocedural follow-up interval was 5 days (range 1-136 days). Twelve magnetic resonance imaging (MRI) measurement parameters (axial and coronal location of the bone block) that could potentially influence graft extrusion were evaluated, along with absolute graft extrusion and relative percentage of extrusion (RPE).

RESULTS

A significant correlation was found between 8 of the 12 MRI measurement parameters and both the absolute extrusion and RPE (r = 0.241-0.438, p < 0.05). The absolute middle distance and depth of the bone block were independent predictors of the absolute extrusion (β = 0.30 and 0.15, respectively; p < 0.05), and the relative middle distance and relative bone-block elevation were found to be predictors of RPE (β = 2.29 and 1.44, respectively; p < 0.05).

CONCLUSION

The rate of graft extrusions after LMAT was high in this study. Both the coronal and axial locations of the bone block were found to influence graft extrusion in LMAT. Therefore, correct positioning of the bone block, including in both the axial and coronal planes, is essential to minimize graft extrusion. Future studies need to investigate the long-term clinical outcome and longevity of extruded menisci after transplantation.

LEVEL OF EVIDENCE

Therapeutic case series, Level IV.

Anatomical study: comparing the human, sheep and pig knee meniscus

BACKGROUND

Animal models are commonly used in investigating new treatment options for knee joint injuries including injuries to the meniscus. The reliability and applicability of these models to replicate findings in humans depends on determining the most suitable animal proxy. Therefore, this study was designed to compare the wet weight, volume and dimensions of the human meniscus with two commonly used animal models: sheep and pig.

METHODS

Human menisci (n = 6 pairs) were obtained from the knee joints of cadaveric male donors. Sheep menisci (n = 6 pairs) and pig menisci (n = 22 pairs) were obtained from the stifle joints of adult sheep and pigs. Meniscal wet weight, volume and dimensions of the body were measured and compared among the species. Anatomical dimensions included circumference, width, peripheral height, articular height and superior articular length.

RESULTS

The circumference of human menisci (lateral: 84.0 mm, medial: 88.7 mm) was significantly longer than that of sheep (lateral: 50.0 mm, medial: 55.5 mm) and pig (lateral: 66.8 mm, medial: 64.9 mm). The majority of the remaining dimensions of the medial and all of the remaining dimensions of the lateral menisci in sheep showed no statistical difference in comparison to the human menisci. The meniscal weight in pig was significantly larger (lateral: 6.4 g, medial: 5.0 g) than the human (lateral: 4.9 g, medial: 4.4 g) and sheep (lateral: 2.5 g, medial: 2.2 g). Porcine meniscal volume (lateral: 6.5 ml, medial: 5.1 ml) was also larger than the human (lateral: 5.0 ml, medial: 4.5 ml) and sheep (lateral: 2.3 ml, medial: 2.2 ml) menisci. The dimensions measured in the pig meniscus were generally larger than human menisci with statistically significant differences in most categories.

CONCLUSION

Sheep meniscal dimensions more closely matched human meniscal dimensions than the pig meniscal dimensions. This information may help guide the choice of an animal proxy in meniscal research.

Which Are the Most Reliable Methods of Predicting the Meniscal Size for Transplantation?

BACKGROUND

Although the size of the meniscal allograft is crucial during meniscal transplantation, the accuracy of meniscal measurement methods is still under debate. A number of methods based on radiographic and magnetic resonance imaging (MRI) data as well as on anthropometric data have been proposed, but their reproducibility and reliability are still unclear.

PURPOSE

To compare meniscal length and width as measured by different techniques (anthropometric and plain radiographic) to establish which of these 2 methods is more reliable and cost-effective for determining the meniscal size in comparison to MRI.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

The MRI scans and plain radiographic films of 22 patients (44 knees) from a single institution were studied. The width and length of the medial and lateral menisci were measured using specific techniques. Data on sex, age, body weight, and height were used to develop a regression formula for meniscal measurements (comparing both imaging methods) to establish meniscal dimensions. Data validation was achieved using the Pearson correlation, the intraclass correlation coefficient, and the Wilcoxon nonparametric test for all variables, with a significance level established at 95%. Accuracy was established as a 10% measure discrepancy from the gold standard (MRI) and was considered an average between the right and left knees.

RESULTS

No statistically significant difference was observed between the right and left knees on radiographic and MRI measurements. The Pollard technique of radiographic measurement overestimated the width of the lateral meniscus when compared with anthropometric measurements (P < .001), considering MRI as the gold standard. The same was observed for MRI measurements of the length of the lateral meniscus in which not only anthropometric but also plain radiographic measurements using the Yoon technique were significantly smaller than those values found with the Pollard technique (P < .001). The anthropometric method underestimated the width and length of the medial meniscus with an accuracy of 68.2% and 63.6%, respectively. The radiographic method was comparable with MRI in establishing all medial meniscal measurements with an accuracy of 93.2% for length and 77.3% for width.

CONCLUSION

Some viable alternatives to MRI have been suggested. For the lateral meniscus, anthropometric data are an alternative for width, and the Yoon method can be used to assess length. For the medial meniscus, the Pollard method is considered a satisfactory alternative. This study emphasized the importance of measuring the width and length of the meniscus independently during preoperative sizing for a meniscal allograft transplantation procedure. Using MRI as a gold standard, the study also proposed other less costly and satisfactory methods of obtaining such measurements.

Meniscus transplantation in skeletally immature patients

Meniscal pathology in skeletally immature patients includes meniscal tears and discoid lateral meniscus. Total or subtotal meniscectomy may occur in patients with discoid lateral meniscus or severe meniscal tears. Meniscal transplantation may be an option in skeletally immature patients status after total or subtotal meniscectomy with knee symptoms or dysfunction. This study focuses on the surgical technique and short-term outcomes of meniscus transplantation in skeletally immature patients. We reviewed our clinical database for skeletally immature patients who had undergone meniscus transplantation with a minimum of 2 years of follow-up. Patients were contacted, invited for a physical exam, and asked to complete a Pedi-IKDC, Lysholm, and Tegner outcomes questionnaire. The study protocol was approved by the responsible institutional review board. Three patients (two females/one male) were eligible for the study, each of whom responded to our invitation indicating availability for physical exam and questionnaire. Two patients had undergone subtotal discoid meniscus resection, leading to early lateral compartment degeneration. One patient developed advanced degeneration after a delay in treatment for a medial bucket-handle tear associated with anterior cruciate ligament rupture. The mean age of the patients at the time of surgery was 12.6±2.3 years. At a mean follow-up of 31±20 months, the mean Pedi-IKDC score was 68.3±4, the mean Lysholm was 55.7±22.3, and the median Tegner was 7 points. There were no indications of growth deformity during the regular postoperative radiological assessments. One patient required subsequent lysis of adhesions along the lateral mini arthrotomy and mobilization under anesthesia. The other two patients were able to return to sports at the same level as before meniscus transplantation and were able to do so within 9 months postoperatively. Over-resection of discoid menisci as well as untreated meniscus injury, the latter typically in conjunction with ligamentous instability, can lead to advanced cartilage degeneration and recalcitrant complaints necessitating surgical treatment before skeletal maturity. We were able to show that meniscus transplantation in skeletally immature patients leads to acceptable clinical outcomes without growth deviation.

LEVEL OF EVIDENCE

IV.

BIORESORBABLE POLYMERIC MENISCAL PROSTHESIS: STUDY IN RABBITS

Objective: To induce growth of a neomeniscus into the pores of a prosthesis in order to protect the knee joint cartilage. Methods: 70 knees of 35 New Zealand rabbits were operated. The rabbits were five to seven months old, weighed 2 to 3.8 kilograms, and 22 were male and 13 were female. Each animal underwent medial meniscectomy in both knees during a single operation. A bioabsorbable polymeric meniscal prosthesis composed of 70% polydioxanone and 30% L-lactic acid polymer was implanted in one side. The animals were sacrificed after different postoperative time intervals. The femoral condyles and neomeniscus were subjected to histological analysis. Histograms were used to measure the degradation and absorption of the prosthesis, the growth of meniscal tissue in the prosthesis and the degree of degradation of the femoral condyle joint cartilage. Results: The data obtained showed that tissue growth histologically resembling a normal meniscus occurred, with gradual absorption of the prosthesis, and the percentages of chondrocytes on the control side and prosthesis side. Conclusion: Tissue growth into the prosthesis pores that histologically resembled the normal rabbit meniscus was observed. The joint cartilage of the femoral condyles on the prosthesis side presented greater numbers of chondrocytes in all its layers.

The Meniscus-Deficient Knee: Biomechanics, Evaluation, and Treatment Options

Meniscal tears are the most common knee injury, and partial meniscectomies are the most common orthopaedic surgical procedure. The injured meniscus has an impaired ability to distribute load and resist tibial translation. Partial or complete loss of the meniscus promotes early development of chondromalacia and osteoarthritis. The primary goal of treatment for meniscus-deficient knees is to provide symptomatic relief, ideally to delay advanced joint space narrowing, and ultimately, joint replacement. Surgical treatments, including meniscal allograft transplantation (MAT), high tibial osteotomy (HTO), and distal femoral osteotomy (DFO), are options that attempt to decrease the loads on the articular cartilage of the meniscus-deficient compartment by replacing meniscal tissue or altering joint alignment. Clinical and biomechanical studies have reported promising outcomes for MAT, HTO, and DFO in the postmeniscectomized knee. These procedures can be performed alone or in conjunction with ligament reconstruction or chondral procedures (reparative, restorative, or reconstructive) to optimize stability and longevity of the knee. Complications can include fracture, nonunion, patella baja, compartment syndrome, infection, and deep venous thrombosis. MAT, HTO, and DFO are effective options for young patients suffering from pain and functional limitations secondary to meniscal deficiency.

Advances and Prospects in Tissue-Engineered Meniscal Scaffolds for Meniscus Regeneration

The meniscus plays a crucial role in maintaining knee joint homoeostasis. Meniscal lesions are relatively common in the knee joint and are typically categorized into various types. However, it is difficult for inner avascular meniscal lesions to self-heal. Untreated meniscal lesions lead to meniscal extrusions in the long-term and gradually trigger the development of knee osteoarthritis (OA). The relationship between meniscal lesions and knee OA is complex. Partial meniscectomy, which is the primary method to treat a meniscal injury, only relieves short-term pain; however, it does not prevent the development of knee OA. Similarly, other current therapeutic strategies have intrinsic limitations in clinical practice. Tissue engineering technology will probably address this challenge by reconstructing a meniscus possessing an integrated configuration with competent biomechanical capacity. This review describes normal structure and biomechanical characteristics of the meniscus, discusses the relationship between meniscal lesions and knee OA, and summarizes the classifications and corresponding treatment strategies for meniscal lesions to understand meniscal regeneration from physiological and pathological perspectives. Last, we present current advances in meniscal scaffolds and provide a number of prospects that will potentially benefit the development of meniscal regeneration methods.

Restoration of the anatomic position during a meniscal allograft transplantation using pre-existing landmarks

INTRODUCTION

Accurate sizing and positioning of a meniscal allograft is an important factor for successful outcomes of meniscal allograft transplantation. The objectives of this study were (1) to search a proper rotational landmark, (2) to determine the sagittal slope of meniscus, and, thus (3) to determine the meniscal positioning.

MATERIALS AND METHODS

A total of 121 consecutive patients who underwent magnetic resonance imaging in the 3 months prior to the beginning of the study were selected. To assess the meniscal rotation, rotation 0° line of the meniscus was defined as a line connecting the center of the anterior and the posterior horn of the medial and lateral meniscus, respectively. At this level, four possible reference lines were compared: Akagi line, line perpendicular to the largest mediolateral dimension (LMLD), line between the medial border of the patellar tendon and the apex of the medial tibial spine (PTMS), and line between the lateral border of the patellar tendon and the apex of the lateral tibial spine. To assess the meniscal slope, the slope of the insertional area, meniscal and bony slopes at the mid-plateau area were compared.

RESULTS

Akagi line was significantly different with a true meniscal rotation (line connecting between centers of the anterior and posterior horns) in both medial and lateral meniscus (p < 0.01 and p < 0.01). LMLD was significantly different in the lateral meniscus (p < 0.01), however, no statistical difference was observed in the medial meniscus (n.s.). PTMS was not different in the medial meniscus (n.s.), however, it was different in the lateral meniscus (p < 0.01). On the medial side, significant statistical difference was observed between insertional and bony slope (p < 0.01) and between meniscal and bony slope (p < 0.01). On the lateral side, comparison of three slopes showed significant statistical differences (p < 0.01-p = 0.03).

CONCLUSION

Line between patellar tendon and tibial spine was a good reference line for a meniscal rotation in the medial meniscus. Among previously introduced reference lines, LMLD showed approximity with a true meniscal rotation. The slope between tibial insertion and mid-portion was significantly different in the lateral meniscus.

Postoperative change in the length and extrusion of the medial meniscus after anterior cruciate ligament reconstruction

PURPOSE

The medial meniscus is a secondary stabilizer of anterior tibial translation in anterior cruciate ligament (ACL)-deficient knees. ACL reconstruction effectively restores an increased anterior tibial translation in the ACL-deficient knee. However, knee osteoarthritis sometimes develops in ACL-reconstructed patients during a long-term follow-up period. We hypothesized that the medial meniscal position would be different between the ACL-deficient and reconstructed knees. The aim of this study was to investigate pre-operative and postoperative location of the medial meniscus in patients who underwent ACL reconstruction.

METHODS

ACL-reconstructed knees (28 knees) and normal knees (27 knees) were investigated. Medial tibial plateau length (MTPL) and medial tibial plateau width (MTPW) were determined using radiographic images. Magnetic resonance imaging (MRI)-based medial meniscal length (MML), medial meniscal width (MMW), and medial meniscal extrusion (MME) were measured. Postoperative change in the MML, MMW, and MME were evaluated and compared with those in normal knees.

RESULTS

No significant differences between the ACL-deficient (pre-operative) and normal groups were noted. The ACL-reconstructed (postoperative) group showed an increase in the MML, in the percentage of the MML (%MML = 100 MML/MTPL), and in the MME. Significant differences between postoperative and normal groups were observed in the MML, %MML, and MME. MMW and MMW percentage (100 MMW/MTPW) were similar in all groups.

CONCLUSIONS

The anteroposterior length and radial extrusion of the medial meniscus increased after ACL reconstruction. Transposition of the medial meniscus may be a possible cause of developing further degenerative knee joint disorders after ACL reconstruction.

3D printing of an extremely tough hydrogel

A super tough hydrogel with tunable mechanical properties was 3D printed.

Meniscal allograft transplantation. Part 1: systematic review of graft biology, graft shrinkage, graft extrusion, graft sizing, and graft fixation

PURPOSE

To provide a systematic review of the literature regarding five topics in meniscal allograft transplantation: graft biology, shrinkage, extrusion, sizing, and fixation.

METHODS

A systematic literature search was conducted using the PubMed (MEDLINE), ScienceDirect, and EBSCO-CINAHL databases. Articles were classified only in one topic, but information contained could be reported into other topics. Information was classified according to type of study (animal, in vitro human, and in vivo human) and level of evidence (for in vivo human studies).

RESULTS

Sixty-two studies were finally included: 30 biology, 3 graft shrinkage, 11 graft extrusion, 17 graft size, and 6 graft fixation (some studies were categorized in more than one topic). These studies corresponded to 22 animal studies, 22 in vitro human studies, and 23 in vivo human studies (7 level II, 10 level III, and 6 level IV).

CONCLUSIONS

The principal conclusions were as follows: (a) Donor cells decrease after MAT and grafts are repopulated with host cells form synovium; (b) graft preservation alters collagen network (deep freezing) and causes cell apoptosis with loss of viable cells (cryopreservation); (c) graft shrinkage occurs mainly in lyophilized and gamma-irradiated grafts (less with cryopreservation); (d) graft extrusion is common but has no clinical/functional implications; (e) overall, MRI is not superior to plain radiograph for graft sizing; (f) graft width size matching is more important than length size matching; (g) height appears to be the most important factor influencing meniscal size; (h) bone fixation better restores contact mechanics than suture fixation, but there are no differences for pullout strength or functional results; and (i) suture fixation has more risk of graft extrusion compared to bone fixation.

LEVEL OF EVIDENCE

Systematic review of level II-IV studies, Level IV.

A systematic review of the incidence and clinical significance of postoperative meniscus transplant extrusion

PURPOSE

To determine the incidence and clinical significance of postoperative meniscus transplant extrusion.

METHODS

A systematic search was performed using PubMed and Cochrane online databases. Inclusionary criteria were English language, clinical trials of meniscus transplantation published from 1984 to 2014, and meniscus extrusion measured on magnetic resonance imaging (MRI).

RESULTS

Twenty-three studies were included, in which 814 menisci were implanted into 803 patients. MRIs were obtained from 2 days to 10 years postoperatively. Eighteen studies used fresh-frozen meniscus transplants implanted with bone (n = 612) or suture fixation (n = 116); four studies, cryopreserved transplants; and one, irradiated transplants. Three measurements assessed extrusion: absolute millimeters of extrusion (0-8.8 mm), relative percentage of extrusion (0-100%), and the percent of transplants that were extruded (0-100 %). Relationships between transplant extrusion and clinical rating scales, joint space narrowing on standing radiographs, and arthrosis progression were inconclusive. Non-anatomic placement of lateral meniscus transplants and suture fixation of medial and lateral transplants were associated with greater extrusion in two studies.

CONCLUSIONS

Inconsistencies among studies prevent conclusions regarding the incidence and clinical significance of meniscus transplant extrusion. Even so, the short- to mid-term results were encouraging for knee function with daily activities and low rates of failure requiring transplant removal. A postoperative MRI showing more than 3-mm extrusion occurring in some studies suggested technique and/or implant sizing problems that required correction. Future studies should report absolute transplant extrusion, relative percent of extrusion, percent of transplant within the tibiofemoral compartment, and the percent of transplants that are extruded.

LEVEL OF EVIDENCE

IV.

The use of contralateral knee magnetic resonance imaging to predict meniscal size during meniscal allograft transplantation

PURPOSE

The purpose of this study was to determine the size of each meniscus and compare it with the contralateral limb using conventional knee magnetic resonance imaging (MRI) taken from previously uninjured, healthy, young volunteers.

METHODS

The knee joints of 60 healthy volunteers (aged 21 to 43 years, 30 men and 30 women) were enrolled in this study. Standard 3.0-T MRI in a controlled setting was used. By use of the mid-coronal images, the height and width of each medial and lateral meniscus were measured. By use of the mid-sagittal images, the height and width of the anterior and posterior horns of each meniscus was measured. The whole length spanning from the most anterior margin to the most posterior margin of each meniscus was also measured. Mean, standard deviation, and 95% confidence interval values were determined for each measurement.

RESULTS

There were 3 incomplete discoid lateral menisci (10%) in men and 2 incomplete discoid menisci (6.7%) in women. The study group with non-discoid knees comprised 27 men and 28 women. The power of this study ranged from 0.57 to 0.66. All values showed good reliability (intraclass correlation coefficient range, 0.887 to 0.974). There were no significant differences between right and left menisci (all P > .05). There were significant differences between genders. All parameters showed significant differences (P < .05) except the medial meniscus width (P = .221).

CONCLUSIONS

In this small subset of patients, there were no differences between right and left meniscal measurements according to MRI. Therefore, when one is performing meniscal allograft transplantation, contralateral knee MRI may be useful to determine the required size. Identifying both the overall width and length of each meniscus is important when preparing an allograft.

CLINICAL RELEVANCE

Contralateral knee MRI may be used for more accurate meniscal size measurement in patients undergoing meniscal allograft transplantation.

Role of mesenchymal stem cells in meniscal repair

Meniscus integrity is the key for joint health of the knee. Therefore, the main goal of every meniscus treatment should be the maintenance of as much meniscus tissue as possible.

Repair of meniscus tears can be achieved by meniscus suture. However, in a recently published meta-analysis, the long-term outcome of meniscus repair showed a mean failure rate of 24%.

In a preclinical trial, locally applied mesenchymal stem cells produced differentiated meniscus-like tissue in meniscus tears indicating that mesenchymal-based cells, harvested from the bone marrow, enhance meniscus healing in critical-size meniscus tears.

Symptomatic meniscus defects offer the option for meniscus transplantation with porous cell free biomaterials, when a complete meniscus rim is available. Cell-free biomaterials, which are actually in clinical application, reveal variable outcome in mid-term results from complete failure to regeneration with meniscus-like tissue.

In several preclinical studies with different critical-size defects in the meniscus, the application of mesenchymal stem cells could significantly enhance meniscus regeneration compared to empty defects or to cell-free biomaterials.

Regenerative treatment of meniscus with mesenchymal stem cells seems to be a promising approach to treat meniscal tears and defects. However it is still not clear, whether the stem cell effect is a direct action of the mesenchymal-based cells or is rather mediated by secretion of certain stimulating factors. The missing knowledge of the underlying mechanism is one of the reasons for regulatory burdens to permit these stem cell-based strategies in clinical practice. Other limitations are the necessity to expand cells prior to transplantation resulting in high treatment costs. Alternative treatment modalities, which use growth factors concentrated from peripheral blood aspirates or mononucleated cells concentrated from bone marrow aspirates, are currently in development in order to allow an attractive one-step procedure without the need for cell expansion in cultures and thus lower efforts and costs.

In summary, Tissue Engineering of meniscus with mesenchymal based cells seems to be a promising approach to treat meniscal tears and defects in order to restore native meniscus tissue. However, advances of the technology are necessary to allow clinical application of this modern regenerative therapy.

3D geometry analysis of the medial meniscus--a statistical shape modeling approach

The geometry-dependent functioning of the meniscus indicates that detailed knowledge on 3D meniscus geometry and its inter-subject variation is essential to design well functioning anatomically shaped meniscus replacements. Therefore, the aim of this study was to quantify 3D meniscus geometry and to determine whether variation in medial meniscus geometry is size- or shape-driven. Also we performed a cluster analysis to identify distinct morphological groups of medial menisci and assessed whether meniscal geometry is gender-dependent. A statistical shape model was created, containing the meniscus geometries of 35 subjects (20 females, 15 males) that were obtained from MR images. A principal component analysis was performed to determine the most important modes of geometry variation and the characteristic changes per principal component were evaluated. Each meniscus from the original dataset was then reconstructed as a linear combination of principal components. This allowed the comparison of male and female menisci, and a cluster analysis to determine distinct morphological meniscus groups. Of the variation in medial meniscus geometry, 53.8% was found to be due to primarily size-related differences and 29.6% due to shape differences. Shape changes were most prominent in the cross-sectional plane, rather than in the transverse plane. Significant differences between male and female menisci were only found for principal component 1, which predominantly reflected size differences. The cluster analysis resulted in four clusters, yet these clusters represented two statistically different meniscal shapes, as differences between cluster 1, 2 and 4 were only present for principal component 1. This study illustrates that differences in meniscal geometry cannot be explained by scaling only, but that different meniscal shapes can be distinguished. Functional analysis, e.g. through finite element modeling, is required to assess whether these distinct shapes actually influence the biomechanical performance of the meniscus.

Postoperative change in medial meniscal length in concurrent all-inside meniscus repair with anterior cruciate ligament reconstruction

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.

Meniscus matching: evaluation of direct anatomical, indirect radiographic, and photographic methods in 10 cadaver knees

INTRODUCTION

When performing meniscus transplantation, allograft size must be carefully matched to the host knee anatomy. The radiographic method devised by Pollard et al. is the current reference standard for meniscus size matching. The primary objective of this study was to compare the accuracy of radiographic measurement according to Pollard, direct anatomic measurement, and photographic measurement.

HYPOTHESIS

Anatomic and photographic allograft size measurement is as reliable as radiographic host-knee sizing according to Pollard et al.

MATERIALS AND METHODS

Three methods for measuring meniscal width and length based on reliable landmarks were assessed in 10 cadaver knees: direct measurement of anatomic specimens, measurement of photographs, and the radiographic method described by Pollard et al.

RESULTS

No significant differences were found between the anatomic and radiographic methods, whereas the anatomic and photographic methods produced significantly different results. Compared to the anatomic method, mean overall measurement error was 7.9% for the radiographic method and 24.1% for the photographic method.

DISCUSSION

The photographic method used in everyday practice during allograft harvesting is not reliable. Correcting for magnification bias might improve the performance of the photographic method. The radiographic method described by Pollard et al. is acceptable, with a margin of error of about 10%, which is considered tolerable. In practice, however, the radiographic method is burdensome to use.

CONCLUSION

The best measurement method is direct measurement of the specimen during allograft harvesting.

LEVEL OF EVIDENCE

Level IV.

Meniscus reconstruction: today's achievements and premises for the future

Injuries of the meniscus remain a burden for the development of premature cartilage degeneration and osteoarthritis. This review surveys all treatment options and focuses on the recent development of tissue engineering. Tissue engineering of the meniscus means a successful combination of cells, scaffolds and specific stimuli. Each element of the combination can be subject to variation. Studies investigating the optimum meniscus implant and previous steps in producing these implants are presented in this article. A comprehensive search of the English and German literature was performed in PubMed to retrieve appropriate manuscripts for review. Based on the literatures, autografts and allografts can delay the progress of osteoarthritis for a restricted time period, but several concerns persist. The biomechanical properties of the native meniscus are not copied entirely by the current existing autografts. Congruence, fixation, biocompatibility and potential infection will always remain as limitations for the users of allografts. Long-term results are still not available for meniscus prosthesis and even though it permits fast recovery, several aspects are questionable: bioincompatibility and a lack of cellular adhesion are likely to compromise their long-term fate. Currently, there is no ideal implant generated by means of tissue engineering. However, meniscus tissue engineering is a fast developing field, which promises to develop an implant that mimics histological and biomechanical properties of the native meniscus. At present several cell sources and scaffolds have been used successfully to grow 3-dimensional constructs. In future, optimal implants have to be developed using growth factors, modified scaffolds and stimuli that support cellular proliferation and differentiation to regenerate the native meniscus more closely.

The tips and pitfalls of meniscus allograft transplantation

When faced with an irrepairable meniscus or a patient who has had a total or subtotal meniscectomy, meniscus allograft transplantation (MAT) is the preferred modality to restore biomechanical function of the meniscus. The indications for meniscus allograft transplantation are yet to be established. However, currently, MAT has previously been indicated for symptomatic patients who have mild or early osteoarthritis, are younger than 50 years of age, and present with an Outerbridge grade II or lower. The short- to intermediate-term results confirmed noteworthy clinical improvements and consistent objective findings. On the other hand, the successful outcome would be reduced by various complications. Therefore, long-term observation required to evaluate the longevity of these results. The purpose of this article is to review the current research of concerns on the results of MAT, and to describe the technical tips and pitfalls so as to successful clinical results.

Intra-articular morphology of the knee joint in children with Blount disease: a case-control study using MRI

BACKGROUND

The clinical and radiographic abnormalities of the lower limb in children with Blount disease are well known. However, there is controversy regarding the intra-articular morphologic changes in the involved knee joint. The purpose of our study was to evaluate the meniscal and articular surface morphology in children with Blount disease with use of magnetic resonance imaging and to compare these findings with similar measurements in a control group.

METHODS

Preoperative magnetic resonance imaging scans of the knee of children with Blount disease were compared with those of a control group. Coronal and sagittal morphometric parameters including the height and width of the menisci, thickness of the unossified proximal tibial epiphysis, tibial condylar and meniscal inclination, and presence of signal changes and/or tears of the menisci were documented.

RESULTS

Twenty-six children (thirty-three) knees with Blount disease (mean age, 10.5 years) and twenty children without Blount disease (mean age, 9.6 years) were identified. The midcoronal medial meniscal height and width were greater in the Blount disease group (p < 0.0001). Abnormal signal changes were noted in the medial meniscus in twelve limbs (39%) in the Blount group and one limb (5%) in the control group (p = 0.008). The mean thickness of the unossified cartilage of the proximal medial tibial epiphysis was also greater in the Blount disease group (p = 0.0005). The morphology of the menisci and unossified cartilage in the lateral compartment did not differ between the two groups. The mean tibial condylar and bimeniscal inclinations in the coronal and sagittal planes were also similar in both groups. In a multivariate regression analysis, only body mass index correlated with the height of the medial meniscus in the coronal plane (p = 0.0035) and of the posterior horn of the medial meniscus in the sagittal plane (p = 0.0037) in children with Blount disease.

CONCLUSIONS

Children with Blount disease have increased thickness of the chondroepiphysis of the proximal medial aspect of the tibia, increased height and width of the medial meniscus, and greater frequency of abnormal signals in the posterior horn of the medial meniscus. These morphologic changes may compensate for the diminished height of the ossified portion of the medial proximal aspect of the tibia in patients with Blount disease.