Meniscal Displacement Research Articles

Dynamic Magnetic Resonance Imaging Protocol: An Effective and Useful Tool to Assess Discoid Lateral Meniscus Instability in Children.

One of the most common symptoms in cases of discoid lateral meniscus (DLM) in children is a "snapping" knee. The clock in extension, followed by a pop in flexion, perceived by the clinician, reflects the meniscal displacement caused by the peripheral meniscocapsular detachment. Standard magnetic resonance imaging (MRI) results in a 40% false-negative rate for detecting this instability. The hypothesis was that a dynamic MRI protocol could reduce the false negative rate and improve the efficiency of the MRI in detecting the direction of instability. Eight DLM knees (8 patients) with snapping knees (grade 2 of Lyon's classification) were included in this monocentric prospective preliminary study in a referral center of pediatric orthopaedic surgery. Every patient underwent a dynamic MRI protocol with both T2-Fat-Sat sagittal and coronal slices, performed "after the clock" and again "after the pop" in a knee with standard 20 degrees of flexion during acquisition. All the MRI data were correlated with an arthroscopic description of the peripheral tear of the DLM according to Ahn's classification to assess for diagnostic accuracy. The standard MRI protocol resulted in a false-negative rate of 50% for detecting the direction of instability. The dynamic MRI protocol allowed the identification of, and classification of the meniscal instability, meniscal shift, and meniscocapsular tear in 8 of 8 patients (0% false-negative rate), perfectly correlated with arthroscopic findings. This preliminary series, although short, allowed us to understand all the types of movements and lesions associated with the child's discoid meniscus. The detailed case analysis showed a strong benefit of such a protocol for planning the surgical suture procedure. The functionality and reliability of the dynamic MRI protocol is a good and method relatively simple method which does not require specific equipment, minimizing any additional cost compared with standard MRI. Level IV.

Comparative analysis of discoid lateral meniscus size: a distinction between symptomatic and asymptomatic cases.

This study evaluated the differences in meniscal sizes and occupancy between symptomatic and asymptomatic patients diagnosed with discoid lateral meniscus (DLM) using magnetic resonance imaging (MRI) to understand how these variations relate to the presence of symptoms and the patients' age. A retrospective review of 98 patients with DLM was conducted, excluding those with meniscal displacement. Both the width and extrusion of DLM and the percentage of the meniscus to the tibia were measured using mid-coronal and mid-sagittal MRI and compared between symptomatic and asymptomatic DLM groups. The relationships among each parameter, meniscal size, and patient age were evaluated. Symptomatic cases were divided into those with and without horizontal tears on MRI to compare the differences in meniscal morphology. A total of 92 knees from 74 patients were included. Sixty-one knees required surgical intervention for symptomatic DLM, while 31 were asymptomatic and included the contralateral side of symptomatic knees. The symptomatic group exhibited larger morphological variations than the asymptomatic group. Moreover, the sagittal meniscal ratio reduced with age in the asymptomatic group (r = - 0.54, p = 0.002) but remained constant in the symptomatic group. The symptomatic cases with horizontal tears demonstrated larger meniscal dimensions and smaller posterior capsule distances than those without tears. Symptomatic patients with DLM had larger knee morphological changes than asymptomatic ones. Age affected the meniscal occupancy in the sagittal plane only in asymptomatic patients. III.

Biomechanical effects of the medial meniscus horizontal tear and the resection strategy on the rabbit knee joint under resting state: finite element analysis.

The biomechanical changes following meniscal tears and surgery could lead to or accelerate the occurrence of osteoarthritis. The aim of this study was to investigate the biomechanical effects of horizontal meniscal tears and different resection strategies on a rabbit knee joint by finite element analysis and to provide reference for animal experiments and clinical research. Magnetic resonance images of a male rabbit knee joint were used to establish a finite element model with intact menisci under resting state. A medial meniscal horizontal tear was set involving 2/3 width of a meniscus. Seven models were finally established, including intact medial meniscus (IMM), horizontal tear of the medial meniscus (HTMM), superior leaf partial meniscectomy (SLPM), inferior leaf partial meniscectomy (ILPM), double-leaf partial meniscectomy (DLPM), subtotal meniscectomy (STM), and total meniscectomy (TTM). The axial load transmitted from femoral cartilage to menisci and tibial cartilage, the maximum von Mises stress and the maximum contact pressure on the menisci and cartilages, the contact area between cartilage to menisci and cartilage to cartilage, and absolute value of the meniscal displacement were analyzed and evaluated. The results showed that the HTMM had little effect on the medial tibial cartilage. After the HTMM, the axial load, maximum von Mises stress and maximum contact pressure on the medial tibial cartilage increased 1.6%, 1.2%, and 1.4%, compared with the IMM. Among different meniscectomy strategies, the axial load and the maximum von Mises stress on the medial menisci varied greatly. After the HTMM, SLPM, ILPM, DLPM, and STM, the axial load on medial menisci decreased 11.4%, 42.2%, 35.4% 48.7%, and 97.0%, respectively; the maximum von Mises stress on medial menisci increased 53.9%, 62.6%, 156.5%, and 65.5%, respectively, and the STM decreased 57.8%, compared to IMM. The radial displacement of the middle body of the medial meniscal was larger than any other part in all the models. The HTMM led to few biomechanical changes in the rabbit knee joint. The SLPM showed minimal effect on joint stress among all resection strategies. It is recommended to preserve the posterior root and the remaining peripheral edge of the meniscus during surgery for an HTMM.

DEVELOPMENT OF A PRE-CLINICAL EXPERIMENTAL MODEL TO MEASURE MEDIAL MENISCUS POSITION DURING A SIMULATED GAIT CYCLE OF THE KNEE JOINT

The aim of this work was to develop a novel, accessible and low-cost method, which is sufficient to measure changes in meniscal position in a whole-knee joint model performing dynamic motion in a knee simulator.An optical tracking method using motion markers, MATLAB (MATLAB, The MathWorks Inc.) and a miniature camera system (Raspberry Pi, UK) was developed. Method feasibility was assessed on porcine whole joint knee samples (n = 4) dissected and cemented to be used in the simulator (1). Markers were placed on three regions (medial, posterior, anterior) of the medial meniscus with corresponding reference markers on the tibial plateau, so the relative meniscal position could be calculated. The Leeds high kinematics gait profile scaled to the parameters of a pig (1, 2) was driven in displacement control at 0.5 Hz. Videos were recorded at cycle-3 and cycle-50. Conditions tested were the capsule retained (intact), capsule removed and a medial posterior root tear. Mean relative displacement values were taken at time-points relating to the peaks of the axial force and flexion-extension gait inputs, as well as the range between the maximum and minimum values. A one-way ANOVA followed by Tukey post hoc analysis were used to assess differences (p = 0.05).The method was able to measure relative meniscal displacement for all three meniscal regions. The medial region showed the greatest difference between the conditions. A significant increase (p < 0.05) for the root tear condition was found at 0.28s and 0.90s (axial load peaks) during cycle-3. Mean relative displacement for the root tear condition decreased by 0.29 mm between cycle-3 and cycle-50 at the 0.28s time-point. No statistically significant differences were found when ranges were compared at cycle-3 and cycle-50.The method was sensitive to measure a substantial difference in medial-lateral relative displacement between an intact and a torn state. Meniscus extrusion was detected for the root tear condition throughout test duration. Further work will progress onto human specimens and apply an intervention condition.

Meniscal Displacement and Loss of Load-Transmission Function After Radial Tear of the Lateral Meniscus in a Porcine Model: New Insights Into the Functional Dynamics of the Injured Meniscus

Background: Meniscal extrusion/translation has been used as an index for meniscal treatment. However, the relationship between meniscal displacement and the degree of meniscal tear or load–transmission function of the lateral meniscus (LM) remains unclear. Purpose: To clarify the relationship between the width of the radial tear of the LM and (1) meniscal displacement or (2) resultant force through the meniscus under axial compressive load in the porcine model. Study Design: Controlled laboratory study. Methods: Eight intact porcine knees with or without a partial radial tear at the midbody of the LM (involving 30%, 60%, or 90% of its width) were investigated. Reflective markers were attached to the outer wall of the anterior, anteromiddle, posteromiddle, and posterior segments of the LM. A 300-N axial load was applied at 2 flexion angles (30° and 60°), and the 3–dimensional forces and trajectories of the knees were recorded. Marker movements were simultaneously tracked using a motion capture camera system. After total meniscectomy of the LM, the recorded knee trajectories were reproduced, and the resultant force through the LM was calculated (a force carried only by the meniscus in response to a load applied to the whole knee joint). Results: At both flexion angles, the change in distance (mean ± SD) between the anterior and posterior markers under load increased significantly more in the anteroposterior direction in LMs with a 90% tear than in intact LMs (30°, 0.4 ± 0.3 vs 1.4 ± 0.8 mm, P = .004; 60°, 0.1 ± 0.7 vs 1.4 ± 1.0 mm, P < .001 [intact vs 90% tear]). The change in distance between the anteromiddle and posteromiddle markers at 30° also significantly increased in LMs with a 90% tear (0.2 ± 0.2 vs 1.3 ± 1.2 mm, P = .02 [intact vs 90% tear]). The resultant force was significantly lower in LMs with a 90% tear than in intact LMs (30°, 125 ± 47 vs 48 ± 20 N, P < .001; 60°, 93 ± 46 vs 43 ± 11 N, P = .002 [intact vs 90% tear]). We found no significant differences in either meniscal displacements or resultant forces between intact LMs and those with 30% or 60% tears. Conclusion: LMs with a 90%-width midbody radial tear lost load–transmission function with their displacement relative to the tibia primarily in the anteroposterior direction in the porcine model. Clinical Relevance: Even 1 mm of displacement after meniscal injury is evidence that the load–transmission function of the meniscus is greatly impaired. When a displaced torn LM is diagnosed in preoperative imaging, meniscal repair surgery should be considered.

Effectiveness of partial eminectomy with meniscorhaphy in surgical treatment of meniscal displacement of temporomandibular joint. One-year prospective study.

Effectiveness of partial eminectomy with meniscorhaphy in surgical treatment of meniscal displacement of temporomandibular joint. One-year prospective study.

A Useful MRI Classification for Symptomatic Discoid Lateral Meniscus

PurposeThe purpose of this study is to classify the discoid lateral meniscus (DLM) according to the signal and shape in magnetic resonance imaging (MRI), and to provide information not only in diagnosis but also in treatment.Materials and MethodsWe reviewed 162 cases who diagnosed with DLM by MRI and underwent arthroscopic procedures from April 2010 to March 2018. Three observers reviewed MRI findings of all cases and predicted arthroscopic tear using three MRI criteria (criterion 1,2 and 3). Among three criteria, the criterion that most accurately predicts arthroscopic tear was selected. Using this criterion, the cases of predicted tear were named group 1. In addition, group 1 was divided into three subgroups (group 1a, 1b and 1c) by deformation or displacement on MRI and arthroscopic type of tear and procedures were analyzed according to these subgroups.ResultsThe intra-meniscal signal change itself (criterion 3) on MRI showed the highest agreement with the arthroscopic tear. No meniscal deformation and displacement on MRI (group 1a) showed no specific type of tear and more cases of meniscal saucerization. The meniscal deformation on MRI (group 1b) showed more simple horizontal tears and more cases of meniscal saucerization. The meniscal displacement on MRI (group 1c) showed more peripheral tears and more cases of meniscal repair and subtotal meniscectomy. Comparing arthroscopic type of tear and type of arthroscopic procedure between three subgroups, there were significant differences in three groups (P < .05).ConclusionsIntra-meniscal signal change itself on MRI is the most accurate finding to predict arthroscopic tear in symptomatic DLM. In addition, subgroup analysis by deformation or displacement on MRI is helpful to predict the type of arthroscopic tear and procedures.

Evaluation of the Peripheral Rim Instability of the Discoid Meniscus in Children by Using Weight-Bearing Magnetic Resonance Imaging.

The aim of the study was to assess the peripheral rim instability and the clinical value of discoid meniscus. We retrospectively studied 79 magnetic resonance imaging (MRI) examinations of discoid meniscus from May 2017 to September 2019. The patient symptoms and physical findings were documented. The patients underwent "dedicated" 0.25 T supine and weight-bearing MRI examination. Finally, all patients underwent arthroscopy. Sound/clicking during motion (P = 0.009) and limited extension (P = 0.044) of subjective symptoms, clunk during motion (P = 0.035), and flexion contracture (P = 0.012) of physical findings were significant predictors of peripheral rim instability. The comparison of the weight-bearing MRI with the supine position MRI demonstrated that the disformed discoid meniscus was shifted significantly and that no shift was displaced centrally (P = 0.001). A correlation between discoid meniscal displacement and the presence of peripheral rim instability in arthroscopy was noted (P < 0.001) using weight-bearing MRI. The clinical symptoms of the patients combined with weight-bearing MRI can determine peripheral rim instability optimally.

Surgical Treatment of Meniscal Extrusion: A Biomechanical Study on the Role of the Medial Meniscotibial Ligaments With Early Clinical Validation.

Background:Meniscal extrusion refers to meniscal displacement out of the joint space and over the tibial margin, altering knee mechanics and increasing the risk of osteoarthritis. The meniscotibial ligaments have been shown to have an important role in meniscal stability. However, it remains unclear whether an isolated lesion of the medial meniscotibial ligaments will result in meniscal extrusion and whether repairing the detached ligament will reduce extrusion.Hypothesis:A lesion of the medial meniscotibial ligament will result in meniscal extrusion, and repairing the joint capsule will eliminate the extrusion by returning the meniscus back to its original position.Study Design:Controlled laboratory study.Methods:Fresh-frozen human cadaveric knees (N = 6) were used for biomechanical testing. The test protocol involved 100 flexion-extension cycles. In full extension, meniscal extrusion was measured using ultrasound, in both an otherwise unloaded state and while subjected to a 10-N·m varus load. Each knee was tested in its native condition (baseline), after creating a detachment of the medial meniscotibial ligament, and finally with the joint capsule repaired using 3 knotless SutureTak anchors. We also performed a retrospective review of 15 patients who underwent meniscotibial ligament repair with a minimal follow-up of 5 weeks (mean, 14 weeks; range, 5-35 weeks).Results:During biomechanical testing, the mean absolute meniscal extrusion at baseline was 1.5 ± 0.6 mm. After creation of the meniscotibial ligament lesion, the mean absolute meniscal extrusion was significantly increased (3.4 ± 0.7 mm) (P < .001). After repair, the extrusion was reduced to 2.1 ± 0.4 mm (P < .001). Clinically, a reduction in absolute meniscal extrusion of approximately 48% was reached (1.2 ± 0.6 vs 2.4 ± 0.5 mm preoperatively; P < .001).Conclusion:This study indicates that the medial meniscotibial ligaments contribute to meniscal stability as lesions cause the meniscus to extrude and that repair of those ligaments can significantly reduce extrusion. Early clinical results using this meniscotibial ligament repair technique support our biomechanical findings, as a significant reduction in meniscal extrusion was achieved.Clinical Relevance:Our biomechanical findings suggest that repair of medial meniscotibial ligaments reduces meniscal extrusion and clinically may improve meniscal function, with the possible long-term benefit of reducing the risk for osteoarthritis.

Evaluation of the anterior meniscal displacement with reduction by High-Resolution Ultrasonography pulsed-wave Doppler mode (PWD). A pilot study

Introduction : The temporomandibular joint disorder (TMD) refers to mandibular dysfunction caused by reduced function of the primary structures that compose the temporomandibular joint (TMJ) or other structures related to the TMJ or by the interaction of these structures with each other. Ultrasound imaging (USI) can not only demonstrate soft tissue alterations but also visualize hard tissue alterations. Pulsed-wave Doppler mode is a widely used technique in the study of movable structures, particularly the vascular system. Material and Methods: 16 patients (32 TMJ) were included in this study, grouped in 10 women’s and 6 men’s) . Extraoral and intraoral examination of the TMJ was realized to detect anterior disc displacement with reduction. Ultrasonography high resolution examination was carried out by LOGIQ e Healthcare ® with a 16 MHz high frequency transducer. A musculoskeletal L8-18i wideband linear array was used for pulsed wave doppler mode examination. Results : Fourteen patients presented anterior disc displacement with reduction, and 2 patients presented normal disc position. When meniscal displacement is detected, PWD mode presents a distinct waveform on the timeline of the exploration. Conclusion : Pulsed-wave Doppler mode provides an advantage in USI, helping to confirm the existence of anterior disc displacement or crepitation. USI is a noninvasive technique with no radiation exposure and permits static and dynamic exploration of the TMJ with a short examination time, low cost, and no contraindications or special patient preparation.

THE EFFECTS OF POSTERIOR TIBIAL MOBILIZATION ON MENISCAL MOVEMENT: AN IN-SITU INVESTIGATION

Anterior knee pain during knee extension may be related to a meniscal movement restriction and increased meniscal load during function. One method of treatment involves the use of manual posterior mobilization of the tibia to specifically target the meniscotibial interface of the knee joint. The purpose of this study was to measure motion at a cadaveric medial meniscus anterior horn during a posterior tibial mobilization. Prospective, multifactorial, repeated-measures laboratory study. Eight unembalmed cadaveric knee specimens were mounted in a custom apparatus and markers were placed in the medial meniscus, tibia and femur. The tibia was posteriorly mobilized in two randomized knee positions (0 degrees and 25 degrees) using three randomly assigned loads (44.48N, 88.96N, and 177.93N). Markers were photographed and digitally measured and analyzed. All load x position conditions produced anterior displacement of the meniscus on the tibia, where the displacement was significant [t (7) = -3.299; p = 0.013] at 0 degrees loaded with 177.93N (mean 0.41 ± 0.35 mm). The results of 2(position) x 3(load) repeated measures ANOVA for meniscotibial displacement produced no significant main effects for load [F (2,14) = 2.542; p = 0.114) or position [F (1,7) = 0.324, p = 0.587]. All load x position conditions produced significant posterior tibial and meniscal displacement on the femur. The 2(position) x 3(load) repeated measures ANOVA revealed a significant main effect for load for both femoral marker displacement relative to the tibial axis [F (2,14) = 77.994; p < 0.001] and meniscal marker displacement relative to the femoral marker [F (2,14) = 83.620; p < 0.001]. Use of a mobilization technique to target the meniscotibial interface appears to move the meniscus anteriorly on the tibia. It appears that this technique may be most effective at the end range position. 2 (laboratory study).

Quantifying meniscal kinematics in dogs.

The dog has been used extensively as an experimental model to study meniscal treatments such as meniscectomy, meniscal repair, transplantation, and regeneration. However, there is very little information on meniscal kinematics in the dog. This study used MR imaging to quantify in vitro meniscal kinematics in loaded dog knees in four distinct poses: extension, flexion, internal, and external rotation. A new method was used to track the meniscal poses along the convex and posteriorly tilted tibial plateau. Meniscal displacements were large, displacing 13.5 and 13.7 mm posteriorly on average for the lateral and medial menisci during flexion (p = 0.90). The medial anterior horn and lateral posterior horns were the most mobile structures, showing average translations of 15.9 and 15.1 mm, respectively. Canine menisci are highly mobile and exhibit movements that correlate closely with the relative tibiofemoral positions. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1710-1716, 2018.

Meniscal allograft subluxations are not associated with preoperative native meniscal subluxations

To determine the relationship between preoperative subluxation of the original menisci and postoperative graft subluxation after lateral meniscal allograft transplantation (MAT). Forty patients who underwent isolated lateral MATs in meniscus-deficient knees with a low-grade chondral lesion (≤ICRS grade 2) were assessed. Lateral subluxation of the native meniscus before meniscectomy and those of remaining meniscal tissue before MAT were measured on mid-coronal MRI scans taken at each time point. Postoperative meniscal subluxation was assessed using MRI at 6months postoperatively, when the full rehabilitation protocols were completed. Correlation analyses were conducted to determine the associations between each of two preoperative lateral displacements and the postoperative graft subluxation. The mean lateral subluxations before primary meniscectomy and before MAT were 0.3±1.0mm and 0.2±0.8mm, respectively. At 6months postoperatively, it was 2.3±1.9mm. There were no significant correlations between the preoperative subluxation at the two preoperative time points and the postoperative extrusion (Spearman rho 2-sided test: ρ=-0.058, (n.s.) for the native meniscus; Pearson r 2-sided test, r=0.309, (n.s.) for the remaining meniscal rim). Between the postoperative nonextruded and extruded groups, there were no significant differences for the preoperative subluxations. There are no associations between preoperative lateral subluxation of the native menisci and postoperative subluxation of meniscal transplants in patients who undergo MAT on the lateral compartment with low-grade arthritic changes. The extrusion phenomenon may be a distinct feature of transplanted menisci rather than an individual characteristic of meniscal displacement. Surgeons need to keep in mind that graft extrusion in nonarthritic knees might occur during transplantation. IV.

Comparison of Medial and Lateral Meniscus Root Tears.

The meniscus root plays an essential role in maintaining the circumferential hoop tension and preventing meniscal displacement. Studies on meniscus root tears have investigated the relationship of osteoarthritis and an anterior cruciate ligament tear. However, few studies have directly compared the medial and lateral root tears. To assess the prevalence of meniscal extrusion and its relationship with clinical features in medial and lateral meniscus root tears, we performed a retrospective review of the magnetic resonance imaging (MRI) results of 42 knee patients who had meniscus posterior horn root tears and who had undergone arthroscopic operations. The presence of meniscal extrusion was evaluated and the exact extent was measured from the tibial margin. The results were correlated with arthroscopic findings. Clinical features including patients’ ages, joint abnormalities, and previous trauma histories were evaluated. Twenty-two patients had medial meniscus root tears (MMRTs) and twenty patients had lateral meniscus root tears (LMRTs). Meniscal extrusion was present in 18 MMRT patients and one LMRT patient. The mean extent of extrusion was 4.2mm (range, 0.6 to 7.8) in the MMRT group and 0.9mm (range, -1.9 to 3.4) in the LMRT group. Five patients with MMRT had a history of trauma, while 19 patients with LMRT had a history of trauma. Three patients with MMRT had anterior cruciate ligament (ACL) tears, while 19 patients with LMRT had ACL tears. The mean age of the patients was 52 years (range: 29–71 years) and 30 years (range: 14–62 years) in the MMRT and LMRT group, respectively. There was a significant correlation between a MMRT and meniscal extrusion (p<0.0001), and between an ACL tear and LMRT (p<0.0001). A history of trauma was significantly common in LMRT (p<0.0001). LMRT patients were significantly younger than MMRT patients (p<0.0001). Kellgren-Lawrence (K-L) grade differed significantly between MMRT and LMRT group (p<0.0001). Meniscal extrusion is common in patients with MMRTs. However, it is rare in patients with LMRTs, which are more commonly associated with a history of trauma and ACL tears.

Medial meniscal displacement and strain in three dimensions under compressive loads: MR assessment

To investigate the 3D displacement and the local strain of the medial meniscus and its attachments under compressive loading. Magnetic resonance imaging (MRI) scans of six porcine knee joints were performed under unloaded and loaded conditions (100% and 200% body weight [BW]). Volumes were registered to obtain a 3D displacement field of the medial meniscus and its attachments, which were divided into five anatomic compartments. Finally, displacements of the center of mass of each compartment and the local strain were analyzed. The meniscus and its attachments significantly displaced by up to 2.6 ± 1.2 mm (P < 0.01) under knee joint loads of 200% BW. An increase of 0.9 mm in the distance between posterior and anterior horn (P < 0.001) was observed. The meniscus and its attachment showed an average radial stretch of 0.6%, an average circumferential stretch of 0.9%, and an average axial compression of 11.6% at 200% BW. High-resolution MRI was successfully combined with image registration to investigate the displacement and strain of the meniscus and its attachments under compression. The results of this study contribute to the basic understanding of meniscal movement which may impact the design of meniscal implants and the validation of finite element models in the future.

Does High Knee Flexion Cause Separation of Meniscal Repairs?

Background: Previous clinical studies comparing nonrestrictive and restrictive protocols after meniscal repair have shown no difference in outcomes; however, some surgeons still limit range of motion out of concern that it will place undue stress on the repair. Hypothesis: Large acute medial meniscal tears will gap during simulated open chain exercises at high flexion angles, and a repaired construct with vertical mattress sutures will not gap. Study Design: Controlled laboratory study. Methods: Tantalum beads were implanted in the medial menisci of 6 fresh-frozen cadaveric knees via an open posteromedial approach. Each knee underwent 10 simulated open chain flexion cycles with loading of the quadriceps and hamstrings. Testing was performed on 3 different states of the meniscus: intact, torn, and repaired. Biplanar radiographs were taken of the loaded knee in 90°, 110°, and 135° of flexion for each state. A 2.5-cm tear was created in the posteromedial meniscus and repaired with inside-out vertical mattress sutures. Displacement of pairs of beads spanning the tear was measured in all planes by use of radiostereometric analysis (RSA) with an accuracy of better than 80 μm. Results: With a longitudinal tear, compression rather than gapping occurred in all 3 regions of the posterior horn of the meniscus (mean ± standard deviation for medial collateral ligament [MCL], –321 ± 320 μm; midposterior, –487 ± 256 μm; root, –318 ± 150 μm) with knee flexion. After repair, meniscal displacement returned part way to intact values in both the MCL (+55 ± 250 μm) and root region (–170 ± 123 μm) but not the midposterior region, where further compression was seen (–661 ± 278 μm). Conclusions: Acute posteromedial meniscal tears and repairs with vertical mattress sutures do not gap, but rather compress in the transverse plane at higher flexion angles when subjected to physiologic loads consistent with active, open kinetic chain range of motion rehabilitation exercises. The kinematics of the repaired meniscus more closely resemble that of the intact meniscus than that of the torn meniscus in regions adjacent to the MCL and the root but not in the midposterior region, where meniscal repair led to increased compression across the tear plane. Clinical Relevance: This study supports the idea that nonrestrictive unresisted open chain range of motion protocols do not place undue stress on meniscal repairs.

SAT0339 Patterns of us changes in degenerative arthritis: Early vs late osteoarthritis of the knee joint

ObjectivesObjective: 1. To assess the patterns of US evaluation of Knee joint osteoarthritis. 2. To evaluate the use of US as a tool for quantitative assessment of knee trochlear cartilage...

The effect of complete radial lateral meniscus posterior root tear on the knee contact mechanics: a finite element analysis

BackgroundIn recent years, with technological advances in arthroscopy and magnetic resonance imaging and improved biomechanical studies of the meniscus, there has been some progress in the diagnosis and treatment of injuries to the roots of the meniscus. However, the biomechanical effect of posterior lateral meniscus root tears on the knee has not yet become clear. The purpose of this study was to determine the effect of a complete radial posterior lateral meniscus root tear on the knee contact mechanics and the function of the posterior meniscofemoral ligament on the knee with tear in the posterior root of lateral meniscus. MethodsA finite element model of the knee was developed to simulate different cases for intact knee, a complete radial posterior lateral meniscus root tear, a complete radial posterior lateral meniscus root tear with posterior meniscofemoral ligament deficiency, and total meniscectomy of the lateral meniscus. A compressive load of 1000N was applied in all cases to calculate contact areas, contact pressure, and meniscal displacements. ResultsThe complete radial posterior lateral meniscus root tear decreased the contact area and increased the contact pressure on the lateral compartment under compressive load. We also found a decreased contact area and increased contact pressure in the medial compartment, but it was not obvious compared to the lateral compartment. The lateral meniscus was radially displaced by compressive load after a complete radial posterior lateral meniscus root tear, and the displacement took place mainly in the body and posterior horn of lateral meniscus. There were further decrease in contact area and increases in contact pressure and raidial displacement of the lateral meniscus in the case of the complete posterior lateral meniscus root tear in combination with posterior meniscofemoral ligament deficiency. ConclusionsComplete radial posterior lateral meniscus root tear is not functionally equivalent to total meniscectomy. The posterior root torn lateral meniscus continues to provide some load transmission and distribution functions across the joint. The posterior meniscofemoral ligament prevents excessive radial displacement of the posterior root torn lateral meniscus and assists the torn lateral meniscus in transmitting a certain amount of stress in the lateral compartment.

Post-surgical unilateral temporomandibular joint dislocation treated by open reduction followed by orthodontic treatment

A case of prolonged unilateral temporomandibular joint (TMJ) dislocation, which was treated by open surgical reduction and post-surgical orthodontic therapy, is presented. A 58-year-old woman presented complaining of facial asymmetry and malocclusion. She had received surgery for a malignant tumour in the right retromolar region 7 years previously. It was considered that contraction of the pterygoid muscle by surgical injury caused anterior meniscal displacement and TMJ dislocation. Since manual manipulation failed, direct open reduction was performed after separation of the lateral pterygoid muscle from the condylar head and removal of the intra-articular scar tissues. Although the condylar head was returned to the glenoid fossa, optimal occlusion was not obtained because of compensatory tooth movement and inclination. Satisfactory occlusion and symmetric facial appearance were brought about by post-surgical orthodontic therapy.

Effects of medial meniscal posterior horn avulsion and repair on meniscal displacement

Medial meniscal posterior root avulsion (MMRA) leads to deleterious alteration of medial joint compartment loading profiles and increased risk of medial degenerative changes. Surgical repair restores more normal biomechanics to the knee. Our hypothesis is that MMRA will cause medial meniscal (MM) extrusion and gap formation between the root attachment site and MM. Meniscal root repair will restore the ability of the meniscus to resist extrusion, and reduce gap formation at the defect. Seven fresh frozen human cadaveric knees were dissected and mechanically loaded using a servo-hydraulic load frame (MTS ®) with 0 and 1800 N. The knees were tested under three conditions: native, avulsed, and repaired. Four measurements were obtained: meniscal displacement anteriorly, medially, posteriorly, and gap distance between the root attachment site and MM after transection and repair. The medial displacement of the avulsed MM (3.28 mm) was significantly greater ( p < 0.001) than the native knee (1.60 mm) and repaired knee (1.46 mm). Gap formation is significantly larger in the avulsed compared to repaired state at 0 ( p < 0.02) and 1800 N ( p < 0.02) and also larger with loading in both avulsed ( p < 0.05) and repaired ( p < 0.02) conditions. Therefore, MMRA results in MM extrusion from the joint and gap formation between the MM root and the MM. Subsequent surgical repair reduces meniscal displacement and gap formation at the defect.