The effect of meniscal tears and resultant partial meniscectomies on the knee contact stresses: a finite element analysis

Knee osteoarthritis (OA) is believed to result from high levels of contact stresses on the articular cartilage and meniscus after meniscal damage. This study investigated the effect of meniscal tears and partial meniscectomies on the peak compressive and shear stresses in the human knee joint. An elaborate three-dimensional finite element model of knee joint including bones, articular cartilages, menisci and main ligaments was developed from computed tomography and magnetic resonance imaging images. This model was used to model four types of meniscal tears and their resultant partial meniscectomies and analysed under an axial 1150 N load at 0° flexion. Three different conditions were compared: a healthy knee joint, a knee joint with medial meniscal tears and a knee joint following partial meniscectomies. The numerical results showed that each meniscal tear and its resultant partial meniscectomy led to an increase in the peak compressive and shear stresses on the articular cartilages and meniscus in the medial knee compartment, especially for partial meniscectomy. Among the four types of meniscal tears, the oblique tear resulted in the highest values of the peak compressive and shear stresses. For the four partial meniscectomies, longitudinal meniscectomy led to the largest increase in these two stresses. The lateral compartment was minimally affected by all the simulations. The results of this study demonstrate meniscal tear and its resultant partial meniscectomy has a positive impact on the maintenance of high levels of contact stresses, which may improve the progression of knee OA, especially for partial meniscectomy. Surgeons should adopt a prudent strategy to preserve the greatest amount of meniscus possible.     

3D finite element model of meniscectomy: changes in joint contact behavior

The goal of this study is to quantify changes in knee joint contact behavior following varying degrees of the medial partial meniscectomy. A previously validated 3D finite element model was used to simulate 11 different meniscectomies. The accompanying changes in the contact pressure on the superior surface of the menisci and tibial plateau were quantified as was the axial strain in the menisci and articular cartilage. The percentage of medial meniscus removed was linearly correlated with maximum contact pressure, mean contact pressure, and contact area. The lateral hemi-joint was minimally affected by the simulated medial meniscectomies. The location of maximum strain and location of maximum contact pressure did not change with varying degrees of partial medial meniscectomy. When 60% of the medial meniscus was removed, contact pressures increased 65% on the remaining medial meniscus and 55% on the medial tibial plateau. These data will be helpful for assessing potential complications with the surgical treatment of meniscal tears. Additionally, these data provide insight into the role of mechanical loading in the etiology of post-meniscectomy osteoarthritis.     

Effect of degree of knee osteoarthritis on balancing capacity after sudden perturbation

This study aimed to assess equilibrium ability after sudden perturbation in patients with moderate and severe unilateral knee osteoarthritis (OA), with regard to age, gender, and lateral dominance. Our clinical trial included 45 female and 45 male healthy elderly subjects, 24 female and 24 male patients with moderate OA (mOA), and 24 female and 24 male patients with severe OA (sOA). Subjects were divided in two age groups: 65-69 and 70-74years. Using an oscillatory platform, we conducted provocation tests and determined the Lehr's damping ratio (D), which represents balancing capacity after sudden perturbation. D values determined for standing on both legs were similar to those of healthy individuals on the dominant limb or for OA patients on the non-affected limb; they were significantly lower for healthy individuals on the non-dominant limb and OA patients on the affected limb. For healthy subjects and mOA patients, D was significantly decreased with age and influenced by gender. sOA patients presented lower D values than other groups under all conditions, which were not influenced by age or gender. Our results demonstrate that OA patients were less capable of responding to perturbations, possibly indicating that they have an increased risk of falling.     

Impact of the method of exposure in total hip arthroplasty on balancing ability in response to sudden unidirectional perturbation in the first six months of the postoperative period

Introduction and objectiveTotal hip arthroplasty affects 3–5% of the elderly population. Therefore, the effectiveness of surgery and the ensuing rehabilitation is of great significance. This study investigated balancing ability in response to sudden unidirectional perturbation changes during the first 6 months of the postoperative period with respect to different methods of joint exposure during the operation (antero-lateral, direct-lateral and posterior to preserve the joint capsule). Our hypothesis is that the results may provide a tool to improve the rehabilitation procedures.Materials and methodsThe dynamic balancing ability of 25 patients with direct-lateral exposure, 22 with antero-lateral exposure and 25 with posterior exposure during a total hip arthroplasty was examined using ultrasound-based provocation tests prior to and at 6 weeks, 12 weeks and 6 months after total hip arthroplasty. The control group was represented by 45 healthy subjects of identical age. The dynamic balancing ability after unidirectional perturbation was characterised by Lehr’s damping ratio calculated from the results of tests performed with the patient standing on both limbs, standing on the affected limb and standing on the non-affected limb.ResultsIn the case of direct-lateral and antero-lateral exposure, Lehr’s damping ratio significantly decreased compared to the preoperative values at 6 weeks postoperatively, but it increased steadily afterwards. Lehr’s damping ratio while standing on the affected limb was significantly lower – even at 6 months postoperatively – than that of the control group. In the case of posterior exposure, Lehr’s damping ratio continuously increased in the postoperative period and corresponded to that of the control group at 6 months after total hip arthroplasty.Discussion and conclusionFor patients operated on using direct-lateral and antero-lateral exposure methods, the dynamic balancing ability continuously improved in the first 6 months of the postoperative period, but the dynamic balancing ability of the affected limb differed from that of the control group. In the case of posterior exposure to preserve the joint capsule the dynamic balancing ability evaluated a more rapidly compared to the other two exposure methods. There was no significant difference in the balancing ability of the control group at 6 months after total hip arthroplasty with posterior exposure. The increasing range of joint motion, muscle development, and the development of the dynamic balancing ability should be taken into account when compiling rehabilitation protocols. Differences related to the method of exposure should be considered when developing the dynamic balancing ability and abandoning therapeutic aids.     

The vascularization of the menisci. Morphological basis for the repair

Degeneration of the knee joint and increase of anterior-posterior tibial displacement are resulting from total meniscectomy, especially in knees with anterior cruciate deficiency. Vascularisation of the meniscus was studied in 12 cadaver knees after latex injection of vessels. Vascularisation of the anterior and posterior horns was found to be much better than that of the body of meniscus. All vessels originated from the popliteal artery, but variably in importance, and formed the perimeniscal and subsynovial network. 11 peripheral meniscus tears (8 freshly injured, 3 ruptures older than 2 months) were repaired by refixation, followed by immobilisation for 6 weeks. Arthroscopy 3 months postoperatively showed complete healing of all tears. Clinical examinations--follow-up for 14 months--showed no signs of rerupture in any of the patients.     

The effect of kinematic and kinetic changes on meniscal strains during gait

The menisci play an important role in load distribution, load bearing, joint stability, lubrication, and proprioception. Partial meniscectomy has been shown to result in changes in the kinematics and kinetics at the knee during gait that can lead to progressive meniscal degeneration. This study examined changes in the strains within the menisci associated with kinematic and kinetic changes during the gait cycle. The gait changes considered were a 5 deg shift toward external rotation of the tibia with respect to the femur and an increased medial-lateral load ratio representing an increased adduction moment. A finite element model of the knee was developed and tested using a cadaveric specimen. The cadaver was placed in positions representing heel-strike and midstance of the normal gait, and magnetic resonance images were taken. Comparisons of the model predictions to boundaries digitized from images acquired in the loaded states were within the errors produced by a 1 pixel shift of either meniscus. The finite element model predicted that an increased adduction moment caused increased strains of both the anterior and posterior horns of the medial meniscus. The lateral meniscus exhibited much lower strains and had minimal changes under the various loading conditions. The external tibial rotational change resulted in a 20% decrease in the strains in the posterior medial horn and increased strains in the anterior medial horn. The results of this study suggest that the shift toward external tibial rotation seen clinically after partial medial meniscectomy is not likely to cause subsequent degenerative medial meniscal damage, but the consequence of this kinematic shift on the pathogenesis of osteoarthritis following meniscectomy requires further consideration.     

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.     

Quantitative comparison of three rat models of Achilles tendon injury: A multidisciplinary approach

The Achilles tendon, while the strongest and largest tendon in the body, is frequently injured. Inconclusive evidence exists regarding treatment strategies for both complete tears and partial tears. Well-characterized animal models of tendon injury are important for understanding physiological processes of tendon repair and testing potential therapeutics. Utilizing three distinct models of rat Achilles tendon injury, the objective of this study was to define and compare the effects and relative impact on tendon properties and ankle function of both tear severity (complete tear versus partial tear, both with post-operative immobilization) and immobilization after partial tear (partial tear with versus without immobilization). We hypothesized that a complete tear would cause inferior post-injury properties compared to a partial tear, and that immediate loading after partial tear would improve post-injury properties compared to immobilization. All models were reproducible and had distinct effects on measured parameters. Injury severity drastically influenced tendon healing, with complete tear causing decreased ankle mobility and tendon mechanics compared to partial tears. One week of plantarflexion immobilization had a strong effect on animals receiving a partial tear. Tendons with partial tears and immobilization failed early during fatigue cycling three weeks post-injury. Partial tear without immobilization had no effect on ankle range of motion through dorsiflexion at any time point compared to the pre-surgery value, while partial tear with immobilization demonstrated diminished function at all post-injury time points. All three models of Achilles injury could be useful for tendon healing investigations, chosen based on the prospective applications of a potential therapeutic.     

Surface analysis of sheep menisci after meniscectomy via infrared attenuated total reflection spectroscopy

Menisci are very important fibrocartilaginous tissue, which maintain biomechanical functions and physiological stabilization of knee joint. Meniscectomy is known as a surgery to recover partial functions from acute meniscus tears. However, the late consequences of total or partial meniscectomy include signs of osteoarthritis and even ligament instability. Infrared attenuated total reflection (IR‐ATR) spectroscopy is a very useful technique, which can reveal molecular characteristics via the analysis of vibrational bands. The present study has employed IR‐ATR spectroscopy to investigate sheep menisci samples after meniscectomy in a label‐free fashion. Several differences of peak absorbance change and peak shift were observed between the native healthy samples and the meniscectomy samples in distinct IR wavenumber regions, such as amide I band, amide II band, C‐H bending band as well as the sugar band region. Combining the results from the collagen protein IR spectra, it can be speculated that six months after meniscectomy collagen fibrils on the incision lose its ordered arrangement and a decrease in the triple helical structure of collagen fibril is observed. In addition, the collagen fibrils and proteoglycan content might also be slight varied after meniscectomy.      

Sex Difference in Contusion of the Medial Femoral Condyle Rim-Association with MRI Occult Meniscal Tears in the ACL Deficient Knee

BackgroundMeniscal tears, specifically lateral meniscal tears, have a larger than expected un-derdiagnosis rate in the presence of an ACL tear. The purpose of our study was to search for an MRI bone contusion pattern associated with MRI occult meniscal tears in patients with an ACL tear, specifically a contusion of the rim of the medial femoral condyle (RMFC). Our hypothesis was that there would be a significant association between RMFC contusions and MRI occult meniscal tears in patients with an ACL tear. We also searched for a difference between sexes with respect to the presence of the RMFC contusion in the setting of an occult meniscal tear. We also categorized the type, size, and location of these occult meniscal tears in the setting of an ACL tear.Methods This was a retrospective study that examined characteristics of occult meniscal tears and their association with a RMFC bone contusion. IRB approval was obtained. The date range of the study was June 2009 through December 2015. 6392 consecutive knee MRI reports in patients with an ACL deficient knee were reviewed. The study group included 22 patients with MRI occult meniscal tears, the control group included 110 patients. Relevant statistical values were calculated.ResultsThe most common type of occult meniscal tears were small radial and small longitudinal tears of the lateral meniscus. Occult meniscal tears were associated with an RMFC contusion in the study group (p=0.0457), particularly in males (p = 0.0003). In males with a torn ACL, the sensitivity of an RMFC contusion for an occult meniscal tear was 80%.ConclusionIn males with an ACL tear, there was a significant association between a contusion of the RMFC and an occult meniscal tear (commonly small radial or small peripheral partial-thickness longitudinal tears). RMFC contusions were reliably identified by radiologists in this study.Level of Evidence: II     

关节镜下不同术式治疗盘状半月板的临床疗效研究

目的:比较分析关节镜下不同术式治疗盘状半月板的临床效果。方法:选取盘状半月板患者85例,其中完全型盘状半月板47例,行完全切除术(A组)23例,行部分切除成形术(B组)24例;不完全性盘状半月板38例,行完全切除术(C组)20例,行部分切除成形术(D组)18例。术后随访观察,膝关节功能评价分别采用国际膝关节文献委员会膝关节评估表(the international knee documentation committee knee evaluation form,IKDC)和Lysholm评分进行。结果:78例患者均得到有效随访。随访时间12-18个月,平均(16.2±3.4)月。术前各组各评分均无显著差异(P0.05)。完全型盘状半月板中,A组术后IKDC和Lysholm评分分别为(92.9±9.7)分、(93.4±8.6)分,优良率为91.3%(21/23),均显著优于B组[(83.5±8.4)分、(82.7±9.2)分、70.8%(17/24)](P0.05)。C组和D组术后各指标比较无显著差异(P0.05)。结论:关节镜下不同术式治疗盘状半月板均可获得较为满意的疗效,但对于完全型盘状半月板而言,采取完全切除术治疗的患者较部分切除成形术者术后疗效具有一定优势。     

Animal models of osteoarthritis

Animal models of osteoarthritis are used to study the pathogenesis of cartilage degeneration and to evaluate potential antiarthritic drugs for clinical use. Animal models of naturally occurring osteoarthritis (OA) occur in knee joints of guinea pigs, mice and other laboratory animal species. Transgenic models have been developed in mice. Commonly utilized surgical instability models include medial meniscal tear in guinea pigs and rats, medial or lateral partial meniscectomy in rabbits, medial partial or total meniscectomy or anterior cruciate transection in dogs. Additional models of cartilage degeneration can be induced by intra-articular iodoacetate injection or by administration of oral or parenteral quinolone antibiotics. None of these models have a proven track record of predicting efficacy in human disease since there are no agents that have been proven to provide anything other than symptomatic relief in human OA. However, agents that are active in these models are currently in clinical trials. Methodologies, gross and histopathologic features and comparisons to human disease will be discussed for the various models.     

Standing on wedges modifies side-specific postural control in the presence of lateral external perturbations

Standing on wedges changes the position in the ankle joints and affects postural stability in the medial-lateral direction. The objective of the study was to investigate the role of wedges and external lateral perturbations on anticipatory (APA) and compensatory postural adjustments (CPA). Ten healthy young participants were exposed to perturbations applied to the lateral part of their right shoulder when standing on a planar surface, on a medial or lateral wedges. Bilateral electromyographic activity of dorsal and ventral postural muscles and the center of pressure (COP) displacement were recorded and analyzed during the APA and CPA phases. When exposed to the lateral perturbation, reciprocal activation of shank muscles was seen on the side of the perturbation while co-contraction of shank muscles was seen on the contralateral side during the APA and CPA phases. Standing on a wedge was associated with decreased magnitudes of co-contraction and reciprocal activation of shank muscles. The COP displacements were smaller in the APA phase and larger in the CPA phase while standing on wedges compared to standing on the planar surface. The outcome of the study provides a basis for future investigations of incorporating wedges in balance re-training paradigms for the elderly or individuals with neurological impairment.     

Animal models of osteoarthritis in an era of molecular biology

Animal models of osteoarthritis (OA) are used to study the pathogenesis of cartilage degeneration and to evaluate potential anti-arthritic drugs for clinical use. In general, these models fall into 2 categories, spontaneous and induced (surgical instability or genetic manipulation). Animal models of naturally occurring OA occur in knee joints of guinea pigs, mice and Syrian hamsters. Commonly utilized surgical instability models include medial meniscal tear in guinea pigs and rats, medial or lateral partial meniscectomy in rabbits, medial partial or total meniscectomy or anterior cruciate transection in dogs. Transgenic models have been developed in mice. These models all have potential use in the study of molecular mechanisms associated with OA development via use of immunohistochemistry, biochemistry and molecular probes to identify altered matrix molecules at different stages in disease progression. Testing of specific types of inhibitors developed through evaluation of matrix changes in the disease process will ultimately help identify key processes which initiate and perpetuate the disease and will lead to discovery of new disease modifying pharmaceutical agents for OA patients. This paper will focus on the discussion of several models which are likely to be useful in the molecular dissection of processes involved in cartilage degeneration.     

Meniscal pathology - the evidence for treatment

Whilst arthroscopic surgery for the treatment of meniscal tears is the most commonly performed orthopaedic surgery, meniscal tears at the knee are frequently identified on magnetic resonance imaging in adults with and without knee pain. The evidence for arthroscopic treatment of meniscal tears is controversial and lacks a supporting evidence base; it may be no more efficacious than conservative therapies. Surgical approaches to the treatment of meniscal pathology can be broadly categorised into those in which partial menisectomy or repair are performed. This review highlights that the major factor determining the choice of operative approach is age: meniscal repair is performed exclusively on younger populations, while older populations are subject to partial menisectomy procedures. This is probably because the meniscus is less amenable to repair in the older population where other degenerative changes co-exist. In middle-aged to older adults, arthroscopic partial menisectomy (APM) may treat the meniscus tear, but does not address the degenerative whole organ disease of knee osteoarthritis. Thus far, there is no convincing evidence that operative approaches are superior to conservative measures as the first-line treatment of older people with knee pain and meniscal tears. However, in two randomised controlled trials (RCTs) approximately one-third of subjects in the exercise groups had persisting knee pain with some evidence of improvement following APM, although the characteristics of this subgroup are unclear. From the available data, a first-line trial of conservative therapy, which includes weight loss, is recommended for the treatment of degenerative meniscal tears in older adults. The exception to this may be when mechanical symptoms, such as knee locking, predominate. Although requiring corroboration by RCTs, there is accumulating evidence from cohort studies and case series that meniscal repair rather than APM may improve function and reduce the long-term risk of knee osteoarthritis in young adults. There is no clear evidence from RCTs that one surgical method of meniscal repair is superior to another.     

Cost-effectiveness study of outpatient physiotherapy after medial meniscectomy.

In a randomised controlled trial comparing the outcome of two groups of men aged 16-45 one group received outpatient physiotherapy after medial meniscectomy and the other did not. In clinical aspects of knee function there was no significant difference between the test group and control group measured at specified intervals up to 26 weeks postoperatively. Similarly, there was no significant difference between the groups in the time taken to return to work or in the mean fall in take-home pay as a result of meniscectomy. The mean cost per patient of providing outpatient physiotherapy in the test group was 23 pounds at 1976 prices. Thus the least costly way of returning male patients aged 16-45 to activity is by not providing routine outpatient physiotherapy after medial meniscectomy. Further randomised controlled trials are, however, required to determine the value of physiotherapy in other age groups and other conditions.     

Architecture of collagen fibers in the meniscus of the human knee joint, with special reference to the medial meniscus and its connection to the articular ligaments]

1. To understand the meniscus-tears the architecture of their collagenic fibers is of interest, particularly so the connection of the fibers of the medial meniscus with the collateral ligament. 2. The ligaments of 12 knee joints have been studied macroscopically and with the aid of thick serial sections under polarized light. 3. The main portion of the tibial collateral ligament passes the articular space without any connection with the capsule or the meniscus. The upper oblique portion of the ligament runs inside the external zone of the meniscus to the posterior attachment of the latter. Immediately inferior to the articular space the oblique fibers have another attachment. 4. The findings in respect of the arrangement of the fibers in the menisci differ from those in earlier studies. Only in the external zone the fibers run approximately parallel to the outer border. After leaving the external zone the fibers run in an arched way through the middle zone. In the internal zone these fibers have nearly a radial direction. 5. The architecture of the menisci is discussed under functional aspects. It does not correspond to a "spring" but to a tendon, which is extended over a hypomochlion. 6. Forms and localisations of meniscus-tears have been discussed under viewpoint of architecture and compared with clinical results: The typical tear of the posterior segment of the medial meniscus is the horizontal cleavage. The present opinion according to which longitudinal tears are the typical meniscus lesion, seems to be doubtful.     

人工泪液对患者玻璃体切除术后泪膜功能的影响

观察玻璃体切除手术后泪膜的变化和应用人工泪液后对泪膜恢复的影响。方法:60例(60眼)行玻璃体切除手术的患者随机分为两组,A组行玻手术后单用妥布霉素地塞米松眼液和眼膏,B组手术后联合应用妥布霉素地塞米松眼液、眼膏和人工泪液Dextran 70 Eye Drops。分别于术前1d,术后3d、7d、14d及30d详细询问患者是否存在干眼症状,并行泪膜破裂时间(Break-Up Time,BUT)、基础泪液分泌试验(Schirmer I test,SIt)、角膜荧光素染色(Cornea Fluorescein Staining,CFS)检查。对结果进行统计学分析。结果:(1)手术前A组和B组的干眼评分、泪膜破裂时间、角膜荧光染色评分、基础泪液分泌试验检查4个项目的检查值经统计学分析无明显差异;(2)术后各个时间点,B组的BUT检查值较A组均增加且差异显著;(3)术后7d和14d,B组的干眼评分和CFS评分较A组减少且差异显著。结论:玻璃体切除术后早期泪膜稳定性明显下降,加用人工泪液后可明显提高术后泪膜稳定性,提示玻璃体切除术后早期使用人工泪液有利于泪膜恢复。     

Partial meniscectomy changes fluid pressurization in articular cartilage in human knees

Partial meniscectomy is believed to change the biomechanics of the knee joint through alterations in the contact of articular cartilages and menisci. Although fluid pressure plays an important role in the load support mechanism of the knee, the fluid pressurization in the cartilages and menisci has been ignored in the finite element studies of the mechanics of meniscectomy. In the present study, a 3D fibril-reinforced poromechanical model of the knee joint was used to explore the fluid flow dependent changes in articular cartilage following partial medial and lateral meniscectomies. Six partial longitudinal meniscectomies were considered under relaxation, simple creep, and combined creep loading conditions. In comparison to the intact knee, partial meniscectomy not only caused a substantial increase in the maximum fluid pressure but also shifted the location of this pressure in the femoral cartilage. Furthermore, these changes were positively correlated to the size of meniscal resection. While in the intact joint, the location of the maximum fluid pressure was dependent on the loading conditions, in the meniscectomized joint the location was predominantly determined by the site of meniscal resection. The partial meniscectomy also reduced the rate of the pressure dissipation, resulting in even larger difference between creep and relaxation times as compared to the case of the intact knee. The knee joint became stiffer after meniscectomy because of higher fluid pressure at knee compression followed by slower pressure dissipation. The present study indicated the role of fluid pressurization in the altered mechanics of meniscectomized knees.