Tibiofemoral contact mechanics following a horizontal cleavage lesion in the posterior horn of the medial meniscus

The purpose of this study was to determine if a horizontal cleavage lesion (HCL) of the posterior horn of the medial meniscus would result in changes to tibiofemoral contact mechanics, as measured by peak contact pressure and contact area, which can lead to cartilage degeneration. To study this, 10 cadaveric knees were tested in a rig where forces were applied (500 N Compression, 100 N shear, 2.5 Nm Torque) and the knee dynamically flexed from ?5° to 135°, as peak contact pressure and contact area were recorded. After testing of the intact knee, a horizontal cleavage lesion was created arthroscopically and testing repeated. The Wilcoxon signed‐rank test was used to determine if there were differences in peak contact pressure and contact area between the intact knee and that with the HCL. A statistically significant increase in peak contact pressure of 13%, on average, and a decrease in contact area of 6%, on average, was noted following the HCL. This suggests that a horizontal cleavage lesion will result in small but statistically significant changes in tibiofemoral contact mechanics which may lead to cartilage degeneration. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:584–590, 2015.

     

关节镜下半月板部分切除加内减压术治疗半月板囊肿

[目的]探讨膝关节镜下半月板部分切除加内减压术治疗半月板囊肿的疗效。[方法]回顾分析本院2002年1月~2005年12月采用膝关节镜下半月板部分切除加内减压术治疗的9例半月板囊肿病人,男3例,女6例;年龄16~54岁,平均(32.5±14.1)岁;病程2个月~2年,平均(13.4±6.8)个月。内侧半月板囊肿1例,外侧半月板囊肿8例。囊肿发生于半月板前角区5例,体部区3例,后角区1例。囊肿部位半月板水平撕裂6例,复杂裂3例。关节镜下确定半月板裂隙和囊肿相通后行半月板部分切除,注意保留半月板边缘,再经半月板裂隙置入刨削器行囊肿内减压切除,切除囊肿壁,扩大囊肿与膝关节腔间的通道。术后指导病人行患肢股四头肌功能锻炼。术后随访时间6~38个月,平均(17.2±9.8)个月,对比其手术前后Lysholm评分,推断治疗结果。[结果]9例病人随访期间均无复发,膝关节疼痛及肿胀症状消失或明显减轻,活动范围恢复正常,未再有弹响和关节交锁,膝关节表面包块消失。无感染、血管神经损伤、关节活动受限等手术并发症发生。Lysholm评分手术前为(70.2±7.8)分,手术后提高至(96.7±3.3)分(t=-9.3868,P=0.000)。[结论]膝关节镜下半月板部分切除加内减压术在保留半月板功能和减少膝关节骨关节炎的发生上具有显著优点,具有创伤小、疗效佳的特点,是治疗半月板囊肿的基本方法。     

MRI analysis of in vivo meniscal and tibiofemoral kinematics in ACL-deficient and normal knees.

The objectives of this study were to analyze simultaneously meniscal and tibiofemoral kinematics in healthy volunteers and anterior cruciate ligament (ACL)-deficient patients under axial load-bearing conditions using magnetic resonance imaging (MRI). Ten healthy volunteers and eight ACL-deficient patients were examined with a high-field, closed MRI system. For each group, both knees were imaged at full extension and partial flexion ( approximately 45 degrees ) with a 125N compressive load applied to the foot. Anteroposterior and medial/lateral femoral and meniscal translations were analyzed following three-dimensional, landmark-matching registration. Interobserver and intraobserver reproducibilities were less than 0.8 mm for femoral translation for image processing and data analysis. The position of the femur relative to the tibia in the ACL-deficient knee was 2.6 mm posterior to that of the contralateral, normal knee at extension. During flexion from 0 degrees to 45 degrees , the femur in ACL-deficient knees translated 4.3 mm anteriorly, whereas no significant translation occurred in uninjured knees. The contact area centroid on the tibia in ACL-deficient knees at extension was posterior to that of uninjured knees. Consequently, significantly less posterior translation of the contact centroid occurred in the medial tibial condyle in ACL-deficient knees during flexion. Meniscal translation, however, was nearly the same in both groups. Axial load-bearing MRI is a noninvasive and reproducible method for evaluating tibiofemoral and meniscal kinematics. The results demonstrated that ACL deficiency led to significant changes in bone kinematics, but negligible changes in the movement of the menisci. These results help explain the increased risk of meniscal tears and osteoarthritis in chronic ACL deficient knees.     

Effects of kneeling on tibiofemoral contact pressure and area in posterior cruciate-retaining and posterior cruciate-sacrificing total knee arthroplasty

The objective of this study was to measure the effect of kneeling on tibiofemoral contact following cruciate-retaining and posterior-stabilized total knee arthroplasty. Five cadaveric knees were tested on a custom testing system that allowed physiologic muscle loading. Three forces were used to simulate nonkneeling, double-stance kneeling, and single-stance kneeling at flexion angles of 90°, 105°, 120°, and 135°. Tibiofemoral contact areas and pressures were measured using the Tekscan (South Boston, MA) system. Kneeling increased contact areas and pressures in both designs with variable significance (P < .05). Moving from double- to single-stance kneeling increased pressures in the cruciate-retaining group but decreased pressures in the posterior-stabilized group (P < .05). Chronic, repetitive kneeling after total knee arthroplasty may increase polyethylene wear due to increased contact areas and pressures.     

Effects of radial tears and partial meniscectomy of lateral meniscus on the knee joint mechanics during the stance phase of the gait cycle—A 3D finite element study

The purpose of the current study was to evaluate influences of radial tears and partial meniscectomy of lateral meniscus on the knee joint mechanics during normal walking by using computational modeling. A 3D geometry of a knee joint of a healthy patient was obtained from our previous study, whereas the data of normal walking were taken from the literature. Cartilage tissue was modeled as a fibril reinforced poroviscoelastic material, whereas meniscal tissue was modeled as a transverse isotropic elastic material. The realistic gait cycle data were implemented into the computational model and the effects of radial tears and partial meniscectemy of lateral meniscus on the knee joint mechanics were simulated. Middle, posterior, and anterior radial tears in lateral meniscus increased stresses by 300%, 430%, and 1530%, respectively, at the ends of tears compared to corresponding areas in the model with intact lateral meniscus. Meniscus tears did not alter stresses and strains at the tibial cartilage surface, whereas partial meniscectomy increased contact pressures, stresses, strains and pore pressures in the tibial cartilage by 50%, 44%, 21%, and 43%, respectively. Increased stresses and strains were observed primarily during the first ～50% of the stance phase of the gait cycle. The present study suggests that anterior radial tear causes the highest risk for the development of total meniscal rupture, whereas partial meniscectomy increases the risk for the development of OA in lateral tibial cartilage. Highest risks for meniscus and cartilage failures are suggested to occur during the loading response and mid‐stance of the gait cycle. In the future, the present modeling may be further developed to offer a clinical tool for aid in decision making of clinical interventions for patients with knee joint injuries. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1208–1217, 2013     

Clinical features of the posterior horn tear in the medial meniscus

Introduction A lower threshold of suspicion is necessary for the appropriate diagnosis of a posterior horn tear in the medial meniscus. In these cases, radial tears or meniscus detachment from its insertion follow minor trauma and precipitate severe knee pain in middle-aged and elderly patients. The purpose of this paper is to demonstrate the key points for diagnosis through examination of the clinical features of this tear.Materials and methods Arthroscopic examination of 250 knees with medial meniscus tears (and no ligamentous injuries; over 40 years old) identified 26 knees (26 tears) with a posterior horn tear. Of these 26 tears, 16 were radial, and 10 were detached.Results Eighty-five percent of patients could recall discrete events that preceded the pain. They described these events as a click or a feeling of shock. Afterwards, most patients complained of severe pain or giving way. Hydrarthrosis involving more than 5 ml was present in 81%. Most radiographs (92%) appeared nearly normal.Conclusion It is important to note that this type of tear of the posterior horn in the medial meniscus is not rare. Because this area is difficult to visualize arthroscopically, it may be overlooked unless the threshold of suspicion is lowered.No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.     

外侧半月板切除术对成人膝关节周围骨密度的影响

目的 观察外侧半月板切除术（lateral meniscectomy,LMT）对膝关节周围骨密度的影响.方法 选择术后患者128例,根据术后时间分为：0～1年组、2～4年组、5～10年组和11～17年组,设对应健侧为对照组,应用双能X线骨密度仪分别测量膝关节周围六个感兴趣区（region of interest,ROI）骨密度,并拍摄术侧膝关节计算机辅助的X线照片（computed roentgenograph,CR）.结果 0～1年组膝关节周围六个ROI骨密度均下降,R1～R4骨密度分别与对照组比较差异有统计学意义（P＜O.01）;术后2～4年组R1～R4骨密度均下降,而R5、R6骨密度有所增加,其中以R1、R3变化显著,分别与对照组比较差异有统计学意义（P＜0.01）;术后5～10年R2骨密度下降,但其余ROI骨密度增加,以外侧ROI骨密度增加明显,分别与对照组比较差异有统计学意义（P＜0.05）;术后11～17年组R1、R3骨密度下降,分别与对应健侧比较差异有统计学意义（P＜0.05）;CR片结果：部分正常,有的表现为骨小梁模糊、密度减低、可见局限性小片状骨质吸收区,有的表现为关节面内侧密度稍低、外侧密度增高,内髁小梁稀少、骨密度减低,股骨外髁骨质增生、轻度膝外翻,胫骨小梁减少、模糊但密度正常.结论 LMT术可引起膝关节周围适应性的骨重构.     

Contribution of tibiofemoral joint contact to net loads at the knee in gait

Inverse dynamics analysis is commonly used to estimate the net loads at a joint during human motion. Most lower‐limb models of movement represent the knee as a simple hinge joint when calculating muscle forces. This approach is limited because it neglects the contributions from tibiofemoral joint contact forces and may therefore lead to errors in estimated muscle forces. The aim of this study was to quantify the contributions of tibiofemoral joint contact loads to the net knee loads calculated from inverse dynamics for multiple subjects and multiple gait patterns. Tibiofemoral joint contact loads were measured in four subjects with instrumented implants as each subject walked at their preferred speed (normal gait) and performed prescribed gait modifications designed to treat medial knee osteoarthritis. Tibiofemoral contact loads contributed substantially to the net knee extension and knee adduction moments in normal gait with mean values of 16% and 54%, respectively. These findings suggest that knee‐contact kinematics and loads should be included in lower‐limb models of movement for more accurate determination of muscle forces. The results of this study may be used to guide the development of more realistic lower‐limb models that account for the effects of tibiofemoral joint contact at the knee. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1054–1060, 2015.     

Magnetic resonance image analysis of meniscal translation and tibio‐menisco‐femoral contact in deep knee flexion

The purpose of this study was to clarify meniscal displacement and cartilage–meniscus contact behavior in a full extension position and a deep knee flexion position. We also studied whether the meniscal translation pattern correlated with the tibiofemoral cartilage contact kinematics. Magnetic resonance (MR) images were acquired at both positions for 10 subjects using a conventional MR scanner. Subjects achieved a flexion angle averaging 139° ± 3°. Both medial and lateral menisci translated posteriorly on the tibial plateau during deep knee flexion. The posterior translation of the lateral meniscus (8.2 ± 3.2 mm) was greater than the medial (3.3 ± 1.5 mm). This difference was correlated with the difference in tibiofemoral contact kinematics between medial and lateral compartments. Contact areas in deep flexion were approximately 75% those at full extension. In addition, the percentage of area in contact with menisci increased significantly due to deep flexion. Our results related to meniscal translation and tibio‐menisco‐femoral contact in deep knee flexion, in combination with information about force and pressure in the knee, may lead to a better understanding of the mechanism of meniscal degeneration and osteoarthritis associated with prolonged kneeling and squatting. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:673–684, 2008     

Lack of posteromedial tibiofemoral congruence at full flexion as a causative factor in isolated medial meniscal tears

The aim of the current study was to investigate posteromedial tibiofemoral congruence at full flexion of the knee in control knee joints and those affected by an isolated medial meniscal tear, to examine whether lack of such congruence was a causative factor in isolated medial meniscal tears. In this study, 1677 knee joints in 875 subjects were evaluated. The joints were classified as a control group (1345 joints), an isolated medial meniscal tear group (224 joints), and a contralateral isolated medial meniscal tear group (108 joints). Posteromedial tibiofemoral congruence was examined on a lateral radiograph of the knee joint at full flexion. The tangent touching the anterior and posterior parts of the articular surface of the medial tibial condyle was assumed to be the X-axis. To evaluate posteromedial tibiofemoral congruence, we measured the angle formed by the tangent that maximized the gradient of the tangent on the articular surface of the medial femoral condyle, and the tangent that maximized the gradient of the tangent on the articular surface of the medial tibial condyle. The mean angle differed significantly between the control and the isolated medial meniscal tear groups, regardless of sex. Isolated medial meniscal tears were found to be strongly related to an abnormally decreased angle, and, therefore, incongruence of the posteromedial tibiofemoral articulation at full flexion was considered to be one of the causes of isolated medial meniscal tears. Received: May 22, 2001/ Accepted: October 24, 2001     

Transection of the medial meniscus anterior horn results in cartilage degeneration and meniscus remodeling in a large animal model

The meniscus plays a central load-bearing role in the knee joint. Unfortunately, meniscus injury is common and can lead to joint degeneration and osteoarthritis (OA). In small animal models, progressive degenerative changes occur with the unloading of the meniscus via destabilization of the medial meniscus (DMM). However, few large animal models of DMM exist and the joint-wide initiation of the disease has not yet been defined in these models. Thus, the goal of this study is to develop and validate a large animal model of surgically induced DMM and to use multimodal (mechanical, histological, and magnetic resonance imaging) and multiscale (joint to tissue level) quantitative measures to evaluate degeneration in both the meniscus and cartilage. DMM was achieved using an arthroscopic approach in 13 Yucatan minipigs. One month after DMM, joint contact area decreased and peak pressure increased, indicating altered load transmission as a result of meniscus destabilization. By 3 months, the joint had adapted to the injury and load transmission patterns were restored to baseline, likely due to the formation and maturation of a fibrovascular scar at the anterior aspect of the meniscus. Despite this, we found a decrease in the indentation modulus of the tibial cartilage and an increase in cartilage histopathology scores at 1 month compared to sham-operated animals; these deleterious changes persisted through 3 months. Over this same time course, meniscus remodeling was evident through decreased proteoglycan staining in DMM compared to sham menisci at both 1 and 3 months. These findings support that arthroscopic DMM results in joint degeneration in the Yucatan minipig and provide a new large animal testbed in which to evaluate therapeutics and interventions to treat post-traumatic OA that originates from a meniscal injury.     

Compressive moduli of the human medial meniscus in the axial and radial directions at equilibrium and at a physiological strain rate

The axial and radial compressive moduli of the human meniscus are important material properties in tibiofemoral joint models, but they have not been determined previously for fresh‐frozen tissue. Our goals were to measure the moduli at equilibrium and at a physiological strain rate, to determine whether the axial and radial compressive moduli are equal for each type of loading, and to determine whether they depend on the region (i.e., anterior, middle, posterior) of the meniscus. Samples from each region from 10 fresh‐frozen human medial menisci were tested in unconfined compression at four strain levels (3%, 6%, 9%, and 12%) at 32%/s, a strain rate determined to be physiologically relevant to walking, and then allowed to reach equilibrium in stress relaxation. At equilibrium, the axial and radial compressive moduli at 12% strain were 83.4 kPa and 76.1 kPa, respectively (p = 0.58), whereas at the physiological strain rate, the axial and radial compressive moduli at 12% strain were 718 kPa and 605 kPa, respectively (p = 0.61). At the physiological strain rate, the modulus increased with increasing strain (79.2 kPa at 3% strain vs. 662 kPa at 12% strain) and the modulus in the anterior region (1,048 kPa at 12% strain) was significantly greater than that in the posterior region (329 kPa at 12% strain) (p = 0.04). Our study supports a plane of isotropy for the material properties of meniscal tissue. However, the material behavior is strongly nonlinear because the compressive modulus is several orders of magnitude smaller than previously reported values for tensile modulus. Further, the compressive modulus depends on the activity of interest (i.e., static such as standing or dynamic such as walking) due to viscoelastic effects, the strain level, and the region of the tissue. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:951–956, 2008     

Effect of partial and complete posterior cruciate ligament transection on medial meniscus: A biomechanical evaluation in a cadaveric model

Background:

The relationship between medial meniscus tear and posterior cruciate ligament (PCL) injury has not been exactly explained. We studied to investigate the biomechanical effect of partial and complete PCL transection on different parts of medial meniscus at different flexion angles under static loading conditions.

Materials and Methods:

Twelve fresh human cadaveric knee specimens were divided into four groups: PCL intact (PCL-I), anterolateral bundle transection (ALB-T), posteromedial bundle transection (PMB-T) and PCL complete transection (PCL-T) group. Strain on the anterior horn, body part and posterior horn of medial meniscus were measured under different axial compressive tibial loads (200-800 N) at 0°, 30°, 60° and 90° knee flexion in each groups respectively.

Results:

Compared with the PCL-I group, the PCL-T group had a higher strain on whole medial meniscus at 30°, 60° and 90° flexion in all loading conditions and at 0° flexion with 400, 600 and 800 N loads. In ALB-T group, strain on whole meniscus increased at 30°, 60° and 90° flexion under all loading conditions and at 0° flexion with 800 N only. PMB-T exihibited higher strain at 0° flexion with 400 N, 600 N and 800 N, while at 30° and 60° flexion with 800 N and at 90° flexion under all loading conditions.

Conclusions:

Partial PCL transection triggers strain concentration on medial meniscus and the effect is more pronounced with higher loading conditions at higher flexion angles.     

Altered signal intensity in the posterior horn of the medial meniscus: an MR finding of questionable significance

Introduction MR imaging has emerged as an important modality in the non-invasive evaluation of osseous and soft-tissue structures in the post-traumatic knee. However, it is sometimes impossible to determine with confidence if a focus of high signal intensity in the meniscus is confined to the substance of the meniscus or if it extends to involve the joint surface. This is a critical differentiation because the latter represents meniscal tears that can be found and treated arthroscopically, whereas the former represents degeneration, intrasubstance tears or perhaps normal variants that are not amenable to arthroscopic intervention. The aim of this study was to investigate the occurrence of such borderline findings in relation to the posterior horn of the medial meniscus and to correlate the arthroscopic results.Materials and methods Sixty-four patients with suspected post-traumatic internal derangements of the knee who underwent MR imaging prior to arthroscopy were evaluated retrospectively. There were 48 men and 16 women. Their mean age was 28.2 years.Results Tears of the posterior horn of the medial meniscus were diagnosed unequivocally (grade 3 signal) in 18 patients and equivocally (grade 2/3 signal) in 10 patients. Arthroscopic correlation revealed 16 tears (89%) in the unequivocal group and only 1 tear (10%) in the equivocal group.Conclusion A meniscal tear is unlikely when MR shows a focus of high signal intensity in the posterior horn of the medial meniscus that does not unequivocally extend to involve the inferior or superior joint surface. An appropriate trial of conservative treatment is recommended in such questionable cases. MR is a useful diagnostic tool—however, it should be used selectively, and in conjunction with history and clinical examination in evaluating internal derangements of the knee.     

The Contact Area and Pressure Distribution Pattern of the Knee: A Study of Normal and Osteoarthrotic Knee Joints

Seven knees were studied to determine the contact area and pressure distribution of the tibiofemoral joint, under various loads and at 0° flexion, using the casting method and special sensor sheets. At a load of 1000N (Newton) the contact area of the knee was 11.5 × lCmm² with menisci and 5.2 × lCmm² without menisci, and the menisci occupied 70 per cent of the total contact area. Peak pressure at 1000N was 3MPa (Mega Pascal) with the menisci and 6MPa without them. the high pressure areas were located on the lateral meniscus as well as on the uncovered part of the articular cartilage of the lateral compartment, and on the uncovered cartilage in the medial compartment. After removal of the menisci the contact area decreased to below one half that of the intact knee and the contact pressure considerably increased. These facts imply that the menisci have load bearing and load spreading functions.

The contact areas were also measured in two osteoarthrotic knees and they were significantly larger than those in normal knees. in these arthrotic knees the menisci seemed to play a less significant role in transmission of weight than in the normal knees.     

Complete tear of the lateral meniscus posterior root is associated with meniscal extrusion in anterior cruciate ligament deficient knees

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

     

膝半月板损伤的临床、MRI及关节镜对比研究

[目的]比较分析膝关节半月板损伤的临床、MRI和关节镜诊断，以提高诊断率。[方法]对本院176例同时行MRI检查及关节镜治疗，且至少临床、MRI或关节镜之一诊断为半月板损伤的患者MRI及病历资料作回顾性对照分析。以关节镜诊断为标准，计算临床和MRI诊断的敏感性、特异性、准确度，应用卡方检验比较临床和MRI诊断与关节镜诊断的差异。[结果]临床诊断的敏感性、特异性、准确度分别为79．3％、26．3％、73．8％；临床诊断与关节镜诊断差异有统计学意义（z。：7．52，P〈0．01）。MRI诊断的的敏感性、特异性、准确度分别为94．1％、92．9％、93．4％；MRI对半月板撕裂的诊断与关节镜诊断差异无统计学意义（x^2=0．375，P〉0．05）。[结论]MRI是诊断半月板破裂极有价值的无创方法，是膝关节镜术前的重要检查。MRI与临床诊断相结合可提高半月板撕裂伤的诊断率，避免不必要的关节镜手术。     

Effect of medial opening wedge high tibial osteotomy on intraarticular knee and ankle contact pressures

High tibial osteotomy (HTO) is a commonly used surgical technique for treating moderate osteoarthritis (OA) of the medial compartment of the knee by shifting the center of force towards the lateral compartment. Previous studies have documented the effects of HTO on the biomechanics of the knee. However, the effects of the procedure on the contact pressures within the ankle joint have not been as well described. Seven cadavers underwent an HTO procedure with sequential 5° valgus realignment of the leg up to 15° of correction. An axial force of up to 550 N was applied and the intraarticular pressure was recorded. Minor valgus realignment of the proximal tibia does not significantly alter the biomechanics of the ankle. However, moderate‐to‐large changes in proximal tibial alignment result in significantly decreased tibiotalar contact surface area and in changes in intraarticular ankle pressures. These findings are clinically relevant, as they provide a biomechanical rationale for the diagnosis and treatment of ankle symptoms in the setting of lower limb malalignment or after alignment correction procedures. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:598–604, 2015.     

Replication of chronic abnormal cartilage loading by medial meniscus destabilization for modeling osteoarthritis in the rabbit knee in vivo

Medial meniscus destabilization (MMD) is a surgical insult technique for modeling osteoarthritis (OA) by replicating chronic abnormal cartilage loading in animal joints in vivo. The present study aimed to characterize the immediate biomechanical effects (ex vivo) and short‐term histological consequences (in vivo) of MMD in the rabbit knee. In a compressive loading test, contact stress distribution in the medial compartment was measured in eight cadaver rabbit knees, initially with all major joint structures uninjured (Baseline), after MMD, and finally after total medial meniscectomy (TMM). Similarly, the effects on sagittal joint stability were determined in an anterior–posterior drawer test. These biomechanical (ex vivo) data indicated that both MMD and TMM caused significant (p < 0.001), distinct (>1.5‐fold) elevation of peak local contact stress in the medial compartment, while leaving whole‐joint stability nearly unchanged. Histological consequences in vivo were assessed in a short‐term (8‐week) survival series of MMD or TMM (five animals for each group), and both caused moderate cartilage degeneration in the medial compartment. The MMD insult, which is feasible through posterior arthrotomy alone, is as effective as TMM for modeling injurious‐level chronic abnormal cartilage loading in the rabbit knee medial compartment in vivo, while minimizing potential confounding effects from whole‐joint instability. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1555–1560, 2013.     

Comparison of osmotic swelling influences on meniscal fibrocartilage and articular cartilage tissue mechanics in compression and shear

Although the contribution of the circumferential collagen bundles to the anisotropic tensile stiffness of meniscal tissue has been well described, the implications of interactions between tissue components for other mechanical properties have not been as widely examined. This study compared the effects of the proteoglycan‐associated osmotic swelling stress on meniscal fibrocartilage and articular cartilage (AC) mechanics by manipulating the osmotic environment and tissue compressive offset. Cylindrical samples were obtained from the menisci and AC of bovine stifles, equilibrated in phosphate‐buffered saline solutions ranging from 0.1× to 10×, and tested in oscillatory torsional shear and unconfined compression. Biochemical analysis indicated that treatments and testing did not substantially alter tissue composition. Mechanical testing revealed tissue‐specific responses to both increasing compressive offset and decreasing bath salinity. Most notably, reduced salinity dramatically increased the shear modulus of both axially and circumferentially oriented meniscal tissue explants to a much greater extent than for cartilage samples. Combined with previous studies, these findings suggest that meniscal proteoglycans have a distinct structural role, stabilizing, and stiffening the matrix surrounding the primary circumferential collagen bundles. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:95–102, 2012