The long-term effects of hyaluronan during development of osteoarthritis following partial meniscectomy in a rabbit model

OBJECTIVE: The long-term effect of hyaluronan (HA) on meniscus remodeling and articular cartilage preservation was assessed during the development of osteoarthritis following partial meniscectomy in a rabbit model. DESIGN: Approximately 60% of the region of each medial meniscus of 20 rabbit knees was excised bilaterally. The left knee joint was treated with five weekly intraarticular injections of 0.3 ml of HA, beginning 1 week after surgery. The right control knee was injected with PBS on the same schedule. Six months after surgery, animals were killed and the medial menisci and tibial articular cartilage were evaluated morphologically, histologically and biochemically. RESULTS: Meniscal regeneration was observed as newly synthesized translucent tissue, and image analysis revealed that the amount of this tissue was significantly greater in the HA-treated menisci than in the vehicle-treated menisci. Safranin-O staining and image analysis revealed the increased presence of glycosaminoglycans in the HA-treated menisci relative to vehicle-treated menisci while vascularity and biochemical parameters (hydration, total GAGs and reducible collagen crosslinks) were statistically similar in HA- and vehicle-treated menisci. Gross morphologic grading with India ink revealed a trend for less deterioration of tibial articular cartilage in the HA group (P=0.09) while Mankin's score of the HA-treated tibial articular cartilage was marginally lower than that of the vehicle group (P=0.06). Biochemical assessments showed a trend for higher total GAGs concentration in the HA-treated articular cartilage when compared to the vehicle treatment group (P=0.06). CONCLUSION: The present study has demonstrated that following partial meniscectomy, treatment with hyaluronan can enhance meniscal regeneration and may inhibit articular cartilage degeneration as long as six months post surgery.     

Biomechanical study on contact pressure in the femoro-tibial joint

To clarify the function of the menisci, dynamic contact pressure in femoro-tibial joints obtained from postmortem or surgical specimens with intact menisci, following partial and total meniscectomy was measured using transistor pressure transducers and Buldon tube pressure gauges. After meniscectomy, the peak contact pressure increased strikingly and contact area decreased markedly. The lower contact pressure after partial meniscectomy than after total meniscectomy is probably one reason why the results of partial meniscectomy are clinically much better than those of total meniscectomy. With flexion of the knee, the region of peak contact pressure shifted posteriorly and high contact pressure was detected below the posterior segment of the medial meniscus. Stress release in articular cartilage varies from region to region, and occurs remarkably after meniscectomy. These findings suggest that the main function of the menisci is load bearing and protection of the cartilage from overload applied to the knee joint.     

Meniscal Replacement With a Silk Fibroin Scaffold Reduces Contact Stresses in the Human Knee

The aim of the current study was to verify if a previously developed silk fibroin scaffold for meniscal replacement is able to restore the physiological distribution of contact pressure (CP) over the articulating surfaces in the human knee joint, thereby reducing peak loads occurring after partial meniscectomy. The pressure distribution on the medial tibial articular surface of seven human cadaveric knee joints was analysed under continuous flexion–extension movements and under physiological loads up to 2,500 N at different flexion angles. Contact area (CA), maximum tibiofemoral CP, maximum pressure under the meniscus and the pressure distribution were analysed for the intact meniscus, after partial meniscectomy as well as after partial medial meniscal replacement using the silk fibroin scaffold. Implantation of the silk fibroin scaffold considerably improved tibiofemoral contact mechanics after partial medial meniscectomy. While the reduced CA after meniscectomy was not fully restored by the silk fibroin scaffold, clinically relevant peak pressures on the articular cartilage surface occurring after partial meniscectomy were significantly reduced. Nevertheless, at high flexion angles static testing demonstrated that normal pressure distribution comparable to the intact meniscus could not be fully achieved. The current study demonstrates that the silk fibroin implant possesses attributes that significantly improve tibiofemoral CPs within the knee joint following partial meniscectomy. However, the failure to fully recapitulate the CAs and pressures observed in the intact meniscus, particularly at high flexion angles, indicates that the implant's biomechanical properties may require further improvement to completely restore tibiofemoral contact mechanics. © 2019 The Authors. Journal of Orthopaedic Research^® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 37:2583–2592, 2019     

Mechanical properties of articular cartilage covered by the meniscus

OBJECTIVE: To investigate the mechanical properties and morphological characteristics of articular cartilage on the tibial plateau of human knees, including the region covered by the meniscus. DESIGN: Using a 1-mm diameter flat-ended cylindrical probe to apply a constant load (0.6 MPa) at specific sites on the tibial plateau, the mechanical properties of articular cartilage were studied using seven cadaver knees. Comparison was made between data obtained by the cartilage covered by the meniscus and that not covered. This was done for both the medial and lateral plateaus. Histological sections of the articular cartilage were also performed to study differences between cartilage from these regions of the tibial plateau. RESULTS: Compared to cartilage that was not covered by the meniscus, the articular cartilage beneath the meniscus showed a significantly (P<0.05) larger modulus by as much as 70%, and was less thick by about 40%. Also, the subchondral bone quantity and calcified layer thickness were observed to be significantly lesser in the regions covered by the meniscus. CONCLUSIONS: Our findings revealed a significant difference between the mechanical properties and associated structures of articular cartilage in the region covered by the meniscus compared with the articular cartilage not covered by the meniscus.     

Evaluation of small intestinal submucosa grafts for meniscal regeneration in a clinically relevant posterior meniscectomy model in dogs

Large meniscal defects are a common problem for which treatment options are limited. Successful meniscal regeneration has been achieved by using grafts of small intestinal submucosa in posterior, vascular meniscal defects in a dog model. This study investigates the long-term effects of a tibial tunnel fixation technique and a clinically based meniscectomy defect on meniscal regeneration using this model. Eight mongrel dogs underwent medial arthrotomy and partial meniscectomy. The dogs were divided into groups based on defect treatment: small intestinal submucosa (n = 4) or meniscectomy (n = 4). Dogs were scored for lameness by subjective scoring postoperatively, sacrificed at 6 months, and assessed for articular cartilage damage, gross and histologic appearance of the operated meniscus, amount of new tissue in the defect, and relative compressive stiffness of articular cartilage. Dogs in the meniscectomy group were significantly (P = .002) more lame than dogs treated with small intestinal submucosa. Small intestinal submucosa-treated joints had significantly (P = .01) less articular cartilage damage than meniscectomy joints. Small intestinal submucosa meniscal implants resulted in production of meniscal-like replacement tissue, which was consistently superior to meniscectomy in amount, type, and integration of new tissue, chondroprotection, and limb function during the study period. Small intestinal submucosa implants may be useful for treatment of large posterior vascular meniscal defects in humans. The tibial tunnel technique used for fixation may have clinical advantages and therefore warrants further investigation.     

Tensile properties of articular cartilage are altered by meniscectomy in a canine model of osteoarthritis.

Loss of or damage to the meniscus alters the pattern of loading in the knee joint and frequently leads to cartilage degeneration and osteoarthritis. The mechanical properties of articular cartilage have been shown to reflect the extent of cartilage degeneration in human osteoarthritis and in experimental models of joint disease, but there is little experimental data documenting changes in cartilage mechanics following meniscectomy. We hypothesized that the tensile properties of the surface zone of articular cartilage are altered following total medial meniscectomy. Twelve mongrel dogs underwent complete resection of the medial meniscus in the right knee, and the femoral cartilage was studied 12 weeks after the operation. We performed uniaxial, tensile stress-relaxation tests to determine the equilibrium tensile modulus of surface-zone cartilage. Water and glycosaminoglycan content were also measured at site-matched locations. The tensile moduli of the cartilage decreased significantly following meniscectomy. The linear region modulus decreased by 40%, from 25.5 +/- 7.7 to 15.3 +/- 7.2 MPa. There was a weak (r = -0.45), but significant, correlation between the linear region modulus and the gross morphological grade for cartilage damage. Water and glycosaminoglycan content did not change following meniscectomy. Composition was not correlated with mechanical properties or morphological grade, suggesting that cartilage structure may play a more important role than composition in determining the mechanical properties. The observed decrease in cartilage material properties provides a quantitative measure of the loss of cartilage function following meniscectomy and reflects a pattern of change that is consistent with damage to the collagen-proteoglycan solid network.     

Trabecular bone strain changes resulting from partial and complete meniscectomy

Previous studies have documented how partial and complete meniscectomy affect articular contact pressure, but changes in load transfer through the complete osteochondral structure of the proximal tibia after partial and complete meniscectomy are not well known. The current study measured trabecular bone strain changes in the medial tibial plateau resulting from partial and complete medial meniscectomy. Midcoronal sections were prepared from knees from cadavers. High quality digital images, made from contact radiographs of loaded samples, were compared with digital images of unloaded samples using in-house software to measure trabecular bone strain. Measurements were made on specimens with an intact medial meniscus, after removal of the inner (2/3) of the meniscus, and after complete meniscectomy. Partial meniscectomy caused minimal increases in trabecular bone strain throughout the proximal tibia. However specimens with complete meniscectomy had significant trabecular bone strain increases. Many patients sustaining meniscus tears are young, therefore, it is important to understand mechanical changes associated with partial meniscectomy. The data suggest partial meniscectomy causes little change in load transfer through the proximal tibia, supporting partial meniscectomy as a good surgical option for patients with meniscus tears.     

The degenerative effects of partial and total resection of the medial meniscus in dogs' knees.

An experimental effort to determine the degenerative effects in the articular cartilage of the knee joint caused by meniscectomy was performed by doing partial and total meniscectomies on the medial compartment of dogs' knees. Gross and microscopic pathological changes in teh articular cartilage were studied by sacrificing the dogs at intervals of three to ten months. Results indicated that meniscectomy is not a benign procedure, and the removal of a meniscus in itself can lead to degenerative changes in the knee joint. Partial meniscectomy leads to less severe degenerative changes with the degree of change directly related to the amount of meniscus removed. In total meniscectomies when meniscus regeneration occurred, the cartilage surfaces where the meniscus had regenerated were protected. The degree of degenerative change was directly related to the amount of fibrocartilage that remained absent. Therefore, the knee menisci function to protect the articular cartilages from degenerative damages, but the exact mechanism of this is unknown.     

Articular cartilage MR imaging and thickness mapping of a loaded knee joint before and after meniscectomy

OBJECTIVE: We describe a technique to axially compress a sheep knee joint in an MRI scanner and measure articular cartilage deformation. As an initial application, tibial articular cartilage deformation patterns after 2 h of static loading before and after medial meniscectomy are compared. METHODS: Precision was established for repeated scans and repeated segmentations. Accuracy was established by comparing to micro-CT measurements. Four sheep knees were then imaged unloaded, and while statically loaded for 2 h at 1.5 times body weight before and after medial meniscectomy. Images were obtained using a 3D gradient echo sequence in a 4.7 T MRI. Corresponding 3D cartilage thickness models were created. Nominal strain patterns for the intact and meniscectomized conditions were compared. RESULTS: Coefficients of variation were all 2% or less. Root mean squared errors of MR cartilage thickness measurements averaged less than 0.09 mm. Meniscectomy resulted in a 60% decrease in the contact area (P=0.001) and a 13% increase in maximum cartilage deformation (P=0.01). Following meniscectomy, there were greater areas of articular cartilage experiencing abnormally high and low nominal strains. Areas of moderate nominal strain were reduced. CONCLUSIONS: Medial meniscectomy resulted in increased medial tibial cartilage nominal strains centrally and decreased strains peripherally. Areas of abnormally high nominal strain following meniscectomy correlated with areas that are known to develop fibrillation and softening 16 weeks after medial meniscectomy. Areas of abnormally low nominal strain correlated with areas of osteophyte formation. Studies of articular cartilage deformation may prove useful in elucidating the mechanical etiology of osteoarthritis.     

Synovial fluid biomarker levels predict articular cartilage damage following complete medial meniscectomy in the canine knee.

The purposes of this study were to document the histological changes present in the tibial plateaus 12 weeks after complete medial meniscectomy in dogs and to determine if synovial lavage fluid biomarker levels are predictive of the severity of joint damage. Twelve adult dogs underwent complete unilateral medial meniscectomy and synovial lavage fluid biomarker levels, including cartilage oligomeric matrix protein (COMP), keratan sulfate (5D4). 3B3(-), and 3B3(+), were measured serially at 4-week intervals. The dogs were euthanized 12 weeks after surgery and each medial and lateral tibial plateau from the meniscectomized and contralateral knees was graded histologically. Histological data were analyzed using principal components analysis, which resulted in 4 factors that explained 70% of the variation in the data. Factor 2 (weighted most heavily by subchondral bone thickness) and Factor 3 (representative of articular cartilage damage) were significantly affected by compartmental site (P < 0.01 for both). Both of these factors were highest in the medial tibial plateau of the meniscectomized knee, and Factor 3 was significantly higher in this site than in the medial tibial plateau of the contralateral knee (P < 0.01). Peak levels of all 4 synovial lavage fluid biomarkers occurred at 4 weeks post-meniscectomy and 4-week minus baseline levels of all biomarkers were significantly correlated with the Factor 3 scores. This study demonstrates that significant articular cartilage damage occurs relatively quickly following complete medial meniscectomy in dogs and establishes the content and criterion validity for these synovial fluid lavage biomarkers in canine meniscectomy as surrogate measures of articular cartilage damage.     

Chondropathy after meniscal tear or partial meniscectomy in a canine model.

A primary goal in considering treatment for meniscal injuries is the preservation of the health of the articular cartilage. However, the chondroprotective effects of various techniques for meniscal injury treatments are unknown. We used a canine model to quantify articular cartilage degeneration in the medial compartment of the canine knee, resulting from a surgically created tear or a partial meniscectomy (PM) of the posterior region of the medial meniscus (each group, n = 10). After sacrifice at 12 weeks, the development of gross chondropathy and the changes in cartilage tensile stiffness were quantified, and correlations between these measurements were examined. Both treatment surgical treatment groups caused significantly greater gross chondropathy as compared to the unoperated contralateral controls. Cartilage tensile stiffness was significantly lower than unoperated controls by nearly 28% in both experimental groups. However, there were no significant differences observed between the gross chondropathy or the cartilage mechanical property changes between the experimental groups. Importantly, the severity of gross chondropathy was found to significantly correlate with the decrement in tensile stiffness properties of the articular cartilage. These findings indicate that significant degeneration of canine articular cartilage develops to a similar degree in the presence of a partially healed meniscus tear or a PM of the knee.     

Need Room to Operate? Partial and Intentional Release of the Knee Medial Collateral Ligament for Medial Meniscal Surgery

Cutting the medial collateral ligament (MCL), even in part, seems counterintuitive. However, medial meniscal surgery is not always easy, and iatrogenic articular cartilage damage can be a complication of partial meniscectomy, meniscus repair, and/or allograft transplantation in a tight knee. Fortunately, partial tears of the MCL tend to heal, and most patients do tolerate iatrogenic, partial MCL tearing without negative long-term sequelae. However, rather than accidentally tearing the MCL during medial meniscal surgery, if you need room to operate, partially release the MCL.     

Induction of osteoarthrosis in the rabbit knee joint

Medial meniscectomy and the creation of "bucket-handle" lesions of the medial meniscus induce mild to moderate osteoarthrotic changes in the knee joints of mature rabbits. The osteoarthrotic lesions studied by gross inspection and histological sections, almost exclusively involve the medial tibial articular cartilage. The pathologic changes begin superficially, pass to the deeper layers, and are characterized by a loss of the glistening of the cartilage surface, peripheral osteophytes, structural irregularities of the matrix, peripheral cloning, hypocellularity, and diminished amounts of glycosaminoglycan. Osteoarthrosis was assessed from 2 to 16 months following surgery using a grading system from 0 (normal) to 15 (severe degeneration). The mean grades at the various time periods studied range from 3.5 to 7. The mild to moderate nature of the osteoarthrosis is shown by the development of the abnormalities without rapid progression to the severely destroyed joints which characterize many other models.     

Articular cartilage degeneration after frozen meniscus and achilles tendon allograft transplantation: experimental study in sheep

Purpose: The purpose of this study was to analyze cartilage degeneration in knees after total medial meniscectomy, transplantation of fresh-frozen meniscus allograft, and Achilles tendon allograft. Type of Study: Experimental study. Methods: We have studied the articular cartilage in the medial compartment of the left knees in 32 sheep aged 5 to 6 months, with 8 animals in each group. The study was performed after meniscectomy (group I), transplantation of fresh-frozen meniscus allograft (group II), use of fresh-frozen Achilles tendon allograft (group III), and in a control group (group IV). For the histologic study, all samples were stained with Masson’s trichrome and Safranine-O. Mankin’s score was applied to grade the histologic damage to the articular cartilage. Results: The group with the greatest number of degenerative changes was group III, followed by groups I and II. The percentage of thickness of cartilage detected by Safranine-O stain was found to be significantly different in both tibia and femur between the control group and the other 3 groups, but not among groups I, II, and III. The immunoreactivity of the articular surfaces in tibia and femur showed notable differences in all the groups. Collagen X was present in the degenerative hypertrophic chondrocytes in the damaged articular surfaces. Conclusions: Meniscal replacement with meniscal and Achilles tendon allografts provides partial protection against articular damage after a meniscectomy.     

Combined Injury to the ACL and Lateral Meniscus Alters the Geometry of Articular Cartilage and Meniscus Soon After Initial Trauma

Combined injury to the anterior cruciate ligament (ACL) and meniscus is associated with earlier onset and increased rates of post-traumatic osteoarthritis compared with isolated ACL injury. However, little is known about the initial changes in joint structure associated with these different types of trauma. We hypothesized that trauma to the ACL and lateral meniscus has an immediate effect on morphometry of the articular cartilage and meniscus about the entire tibial plateau that is more pronounced than an ACL tear without meniscus injury. Subjects underwent magnetic resonance imaging scanning soon after injury and prior to surgery. Those that suffered injury to the ACL and lateral meniscus underwent changes in the lateral compartment (increases in the posterior–inferior directed slopes of the articular cartilage surface, and the wedge angle of the posterior horn of the meniscus) and medial compartment (the cartilage-to-bone height decreased in the region located under the posterior horn of the meniscus, and the thickness of cartilage increased and decreased in the mid and posterior regions of the plateau, respectively). Subjects that suffered an isolated ACL tear did not undergo the same magnitude of change to these articular structures. A majority of the changes in morphometry occurred in the lateral compartment of the knee; however, change in the medial compartment of the knee with a normal appearing meniscus also occurred. Statement of clinical significance: Knee injuries that involve combined trauma to the ACL and meniscus directly affect both compartments of the knee, even if the meniscus and articular cartilage appears normal upon arthroscopic examination. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:759-767, 2020     

Simultaneous changes in bone mineral density and articular cartilage in a rabbit meniscectomy model of knee osteoarthrosis

OBJECTIVE: It was hypothesized that increased bone mineral density of the medial proximal tibia would precede or coincide with the development of more severe cartilage changes after meniscectomy. METHODS: In a rabbit knee model, mineral density of subchondral bone and changes of articular cartilage were monitored 13 to 40 weeks after medial meniscectomy or a sham operation. RESULTS: Both procedures resulted in a decrease of bone mineral density, especially of the medial proximal tibia, which persisted up to 40 weeks (P< 0.02-0.0007). Meniscectomy induced cartilage changes typical for osteoarthrosis (P< 0.009), which progressed over time on the posterior aspect of the medial tibial plateau (P< 0.009), which is physiologically covered by the meniscus, but the procedure also induced iatrogenic changes which were located mainly on the anterior aspect of the concerned compartment, and which did not progress or develop to osteoarthrosis. CONCLUSIONS: The data suggest that the cartilage changes after meniscectomy in this animal model are caused by the surgical trauma, subsequent limb misuse, and altered load distribution, and initially associated by a decrease not an increase in bone mineral density of the proximal tibia. Moreover, the cartilage changes progressed without a simultaneous increase of the bone mineral density at corresponding sites.     

MRI Evaluation of Isolated Arthroscopic Partial Meniscectomy Patients at a Minimum Five-Year Follow-up

Background The risk of radiographic knee degeneration after partial or total meniscectomy is well documented, but no prior study has employed cartilage-sensitive MRI technology to assess degenerative changes after meniscectomy. Hypothesis Arthroscopic partial meniscectomy results in early articular cartilage wear and subchondral bony degeneration, even in the absence of clinical symptoms, and these findings can be evaluated with cartilage-sensitive MRI. Study design Retrospective cohort. Methods Twenty-nine patients (ages: 15–40) who had undergone isolated arthroscopic partial medial or lateral meniscectomy with at least 5-year follow-up were evaluated. All patients had arthroscopically normal articular cartilage at the time of initial meniscectomy. Seventeen patients (18 knees) underwent partial medial meniscectomy (MM) and 12 patients underwent partial lateral meniscectomy (LM) with mean follow-up of 8.4 and 7.1 years, respectively. Follow-up evaluation included physical examination, outcome questionnaires, and cartilage-sensitive MRI examination with modified Outerbridge grading of articular surfaces. Results Outerbridge grades II–IV were noted in 64% of medial compartment joint surfaces in group MM knees versus 33% of lateral compartment joint surfaces in group LM knees. Abnormal cartilage surfaces (grades II–IV), subchondral sclerosis, and condylar squaring were all significantly more frequent after medial meniscectomy (p < 0.05). Groups MM and LM had no significant differences among outcome scores, which remained excellent in both groups. A significant negative correlation was found between the severity of cartilage wear and functional scoring in the MM group, suggesting that functional disability lags behind early MRI evidence of degeneration. Conclusions Despite optimal preoperative prognostic factors and excellent functional outcomes, MRI evidence of early articular cartilage degeneration was present in both partial medial and lateral meniscectomy patients at a minimum 5-year follow-up. Results support the use of cartilage-sensitive MRI as a noninvasive screening technique to evaluate cartilage changes after arthroscopic partial meniscectomy and may help to counsel the high-risk patient in regard to postoperative activity.     

Lateral meniscus and lateral femoral condyle cartilage injury by retained cement after medial unicondylar knee arthroplasty

The authors experienced an unusual case of a patient with a complex tear of the lateral meniscus and adjacent lateral femoral condyle cartilage injury in the contralateral compartment by retained cement, possibly located at the posteromedial side of the medial tibial component after unicondylar knee arthroplasty. Arthroscopic partial meniscectomy and cartilage microfracture were successfully performed. Two small cement fragments were removed from the posterolateral compartment. A sharp pain in the lateral side disappeared postoperatively and posterior knee pain was much reduced.     

Meniscal allograft transplantation for symptomatic knee after meniscectomy of torn discoid medial meniscus: Report of three cases

In symptomatic discoid medial meniscus, partial meniscectomy is the principal treatment method and can yield promising short-term results. However, unlike the nondiscoid meniscus, discoid medial meniscus is frequently associated with horizontal cleavage tears, attributable to the presence of myxoid degeneration in the intrameniscal substance, in that it may potentially occur deteriorating long-term results because of re-tearing of remaining meniscus or secondary degeneration of cartilage of the medial compartment after meniscectomy. We experienced three rare cases of retear or secondary degeneration of cartilage of the medial compartment after meniscectomy for two patients with torn bilateral meniscus. Both patients were highly active young males. Meniscal allograft transplantation in complicated discoid medial meniscus was performed. At 2 years after meniscal allograft transplantation, clinical outcomes were improved with a normal range of motion. Orthopedic surgeons should recommend activity modification to prevent possible complicated injury of the discoid medial meniscus. Meniscal allograft transplantation may be an alternative option in highly active young patients undergoing complicated discoid medial meniscus to diminish pain, improve knee function, and prevent or delay degeneration.