Collagen 1 gel may improve the regenerative capacity of minced adult and preosteoarthritic cartilage.

PURPOSE: Minced cartilage implantation (MCI) is an evolving technique for the treatment of osteochondral lesions. It was hypothesised that mincing of cartilage may affect chondrocyte viability and phenotype and that embedding in collagen 1 gel results in an improved outcome. The objective of this study was to evaluate the impact of cartilage mincing and whether collagen 1 gel mediates beneficial effects on the chondrocyte phenotype and viability. METHODS: Human cartilage samples from 11 patients undergoing total knee arthroplasty were collected and minced according to the MCI protocol. Minced cartilage was cultured for 1 week with and without embedding in collagen 1 gel and was compared with unminced cartilage flakes as control. Quantitative reverse transcription-PCR and immunohistochemical staining for the chondrocyte marker genes SOX9, COL2, ACAN, COL10 and MMP13 were used to examine the chondrocyte phenotype. Cell death was assessed by the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. RESULTS: Increased chondrocyte cell death of cultured cartilage after mincing was observed. Chondrocytes from minced cartilage exhibited significantly decreased expression and protein levels of homeostatic and hypertrophic chondrocyte markers. Embedding in collagen 1 gel showed no positive effect on viability. However, remarkable is the increased expression of ACAN and the preserved protein level of SOX9 in the collagen 1-embedded minced cartilage. CONCLUSIONS: This study shows that the mincing of cartilage leads to increased chondrocyte death and decreased expression of chondrocyte phenotypic marker genes after 7 days. The use of collagen 1 gel may improve the stability of the phenotype, which needs to be further elucidated. LEVEL OF EVIDENCE: Level III (therapeutic).

[Focal femoral resurfacing and unicompartmental knee replacement : Between osteotomy and total knee replacement]. / Fokaler Oberflächenersatz und unikompartimenteller Gelenkersatz : Im Grenzbereich zwischen Achskorrektur und Totalendoprothetik.

Unicompartmental knee arthroplasty, especially for both femorotibial compartments of the knee, is an established partly joint-saving treatment option for osteoarthritis of the knee if the disease is limited to one compartment. Even smaller implants or resurfacing of the patellofemoral joint have been shown-in smaller patient collectives-to have the potential to yield good clinical results.

Intra- and postoperative assessment of femoral component rotation in total knee arthroplasty: an EKA knee expert group clinical review.

PURPOSE: Malrotation of the femoral component after primary total knee arthroplasty (TKA) is one of the most important problems leading to painful TKA requiring revision surgery. METHODS: A comprehensive systematic review of the literature was performed to present current evidence on how to optimally place the femoral component in TKA. Several landmarks and techniques for intraoperative determination of femoral component placement and examination of their reliability were analyzed. RESULTS: 2806 articles were identified and 21 met the inclusion criteria. As there is no unquestioned gold standard, numerous approaches are possible which come along with specific advantages and disadvantages. In addition, imaging modalities and measurements regarding postoperative femoral component rotation were also investigated. Femoral component rotation measurements on three-dimensional (3D) reconstructed computerised tomography (CT) images displayed intraclass correlation coefficients (ICC) above 0.85, significantly better than those performed in radiographics or two-dimensional (2D) CT images. Thus, 3D CT images to accurately evaluate the femoral prosthetic component rotation are recommended, especially in unsatisfied patients after TKA. CONCLUSION: The EKA Femoral Rotation Focus Group has not identified a single best reference method to determine femoral component rotation, but surgeons mostly prefer the measured resection technique using at least two landmarks for cross-checking the rotation. LEVEL OF EVIDENCE: III.

The menisci and articular cartilage: a life-long fascination.

The menisci and articular cartilage of the knee have a close embryological, anatomical and functional relationship, which explains why often a pathology of one also affects the other.Traumatic meniscus tears should be repaired, when possible, to protect the articular cartilage.Traumatic articular cartilage lesions can be treated with success using biological treatment options such as microfracture or microdrilling, autologous chondrocyte transplantation (ACT), or osteochondral transplantation (OCT) depending on the depth and area of the lesion.Degenerative cartilage and meniscus lesions often occur together, and osteoarthritis is already present or impending. Most degenerative meniscus lesions should be treated first conservatively and, after failed conservative treatment, should undergo arthroscopic partial meniscus resection. Degenerative cartilage lesions should also be treated conservatively initially and then surgically; thereby treating the cartilage defect itself and also maintaining the axis of the leg if necessary.Tears of the meniscus roots are devastating injuries to the knee and should be repaired e.g. by transtibial re-fixation.The clinical role of 'ramp' lesions of the meniscus is still under investigation. Cite this article: EFORT Open Rev 2020;5:652-662. DOI: 10.1302/2058-5241.5.200016.

Screw Track Osteolysis in the Cementless Total Knee Replacement Design.

BACKGROUND: There is a paucity of reports on osteolysis associated with tibial screw fixation in cementless total knee arthroplasty (TKA), and the pathophysiology is not clear. This study aimed to describe the pathology related to screw track osteolysis around the tibia in cementless TKA. METHODS: The study cohort comprised 100 revised cementless TKAs with tibial screw fixation. Screw track osteolysis and various screw angles were analyzed radiologically. Tissue samples from the joint capsule and the osteolytic cavity were investigated for metal/polyethylene wear. The type of tissue response was determined using immunohistochemistry. Retrieved tibial polyethylene inserts were analyzed for screw hole impression and mode of wear. Tissue metal content was measured by inductively coupled plasma optical emission spectrometry. Electrochemical reactions between the tibial tray and the cancellous screws were investigated. RESULTS: Radiological analysis showed screw track osteolysis predominantly at the medial aspect of the tibial component, and the severity of osteolysis positively correlated with smaller medial proximal tibial screw angles. Osteolysis was associated with high titanium concentrations but not with polyethylene particles. An open circuit potential between the screw and the tibial base plate was measured. Necrosis, osteolytic cyst formation and macrophages, T and B cells, and dendritic cells were present. CONCLUSION: The present study highlights the risk for screw track osteolysis in cementless TKA with screw fixation. Our data collectively suggest that titanium wear may contribute to screw track osteolysis in the cementless TKA design. The contribution of screw angles is difficult to prove.

Assessment of Low-Grade Meniscal and Cartilage Damage of the Knee at 7 T: A Comparison to 3 T Imaging With Arthroscopic Correlation.

OBJECTIVES: The aim of this study was to compare the assessment of low-grade meniscal tears and cartilage damage in ultrahigh-field magnetic resonance imaging (MRI) at 7 T to routine clinical MRI at 3 T. MATERIALS AND METHODS: This study was approved by the local ethics committee, and written informed consent was obtained from each patient. Forty-one patients with suspected meniscal damage or mild osteoarthritis (Kellgren-Lawrence score, 0-2) received 7 T as well as routine clinical 3 T consecutively. The imaging protocol at both field strengths consisted of PD-weighted imaging with more than doubled resolution at 7 T. Images were read blinded regarding field strength and patient characteristics by 3 readers with different experience in musculoskeletal MRI (3 years, 6 years, and 10 years) according to a modified whole-organ MRI score of the knee in osteoarthritis and the Score of the International Cartilage Repair Society. Arthroscopic reports as a criterion standard were available for 12 patients. A multifactorial mixed model analysis was performed. RESULTS: The mean cumulated diagnostic score at 7 T was significantly closer to the criterion standard compared with 3 T in patients where criterion standard was available (P < 0.001). In all 41 patients, the damages were rated more severely at 7 T reflected by a mean higher cumulative score in cartilage (P < 0.001) and in the meniscus (P < 0.001). No difference in interreader variability between 3 T and 7 T was observed. Imaging acquisition time was nearly identical. CONCLUSIONS: Morphologic imaging of cartilage and meniscal damage of the knee in ultrahigh-field MRI at 7 T with PD-weighted TSE sequences seemed to have a significantly higher diagnostic accuracy than 3 T and can be performed with equal acquisition times while exploiting higher resolution of 7 T.

Stiffness of meniscus tissue depends on tibio-femoral load and structural integrity of the meniscus root.

Development of meniscus replacements requires in-depth knowledge of the material properties and biomechanical behavior of the native meniscus. The compressive properties are of particular interest in this context, which are often assessed with indentation tests. However, those tests are usually done on isolated tissue specimens ex situ, which could have a significant impact on the results. It was, therefore, the goal of the study to assess the stiffness of the meniscus tissue in situ in porcine specimens and to compare it to that of artificial substitutes. Porcine knees (n = 8) were prepared such that the medial meniscus periphery was exposed and the knees could be mounted in a materials testing machine. The tissue stiffness was than measured on the meniscus periphery using a Shore-A durometer in (1) the unloaded knee, (2) with 500-N tibio-femoral compressive load, and (3) with 500-N tibio-femoral load and the posterior meniscus root detached. The stiffness of the meniscus tissue was significantly increased when tibio-femoral load was applied, while this effect was lost when the meniscus root was cut (average measurements on a 0-100 Shore-A durometer scale: group A, 33.8; group B, 58.4; and group C, 36.2). Polyurethane and collagen meniscus implants showed an inferior stiffness compared to the native meniscus. These findings might be relevant for the material choice in artificial meniscus replacements and the fixation of allografts. Biomechanical testing of isolated tissue specimens could underestimate the effective meniscus tissue stiffness compared to a physiological joint environment.

Interference screw fixation of free tendon grafts: significant time-dependent decrease of the initial contact forces.

PURPOSE: Interference screw fixation of tendon grafts is a common practice in ACL surgery. Tissues like tendons and bone show a complex viscoelastic behaviour, which could affect the contact forces in interference screw fixation. These effects are not well investigated, especially over prolonged periods of time. The time-dependent behaviour of tendons was thus the subject of the study. It was our hypothesis that a substantial decrease of the contact forces will be observed. METHODS: Using an artificial bone surrogate and pig tendons, the time-dependent behaviour of the contact force in a simulated interference screw fixation was investigated over a 12-h period. As the screwing in can have deleterious effects on tendons, two scenarios, screwing in (A) and pressing the screw against the tendon (B), were investigated. RESULTS: The initial contact forces showed a magnitude of 1,299 N (A) and 2,156 N (B), respectively. A significant decrease to 530 N (A) and 461 N (B) after 12 h was observed (p < 0.001). However, more than 80 % of the relaxation occurred during the first hour. CONCLUSION: Significant relaxation of the contact force in interference screw fixation of ACL grafts occurs, which has implications for research and clinical practice. The strength of ACL fixation methods should not be assessed immediately after assembly of the specimens and comparisons should be done only when the same time intervals from assembly to testing were used. Also, in clinical practice, the initial fixation strength will probably not be maintained. Therefore, a backup fixation might be advisable.

Autologous proliferative therapies in recalcitrant lateral epicondylitis.

OBJECTIVE: This study investigates the clinical effects of autologous conditioned plasma (ACP) injections and low-level laser application as therapy options for chronic lateral epicondylitis. DESIGN: A total of 52 patients with chronic lateral epicondylitis were evaluated in this study; 26 of these patients received three ACP injections and the control group, with 26 patients, received 12 laser applications, with standardized physical therapy for all patients afterward. Control examinations took place before treatment, after 2 and 6 mos, and in the 1 yr final follow-up. The control examination included the visual analog scale for pain and Disabilities of the Arm, Shoulder and Hand outcome measure scores. RESULTS: The analysis at final follow-up after 1 yr showed that both treatment options resulted in successful therapy outcome for the patients. In total, 63.5 % were successfully treated. Successful treatment was defined as more than 30% improvement in the visual analog score and more than 10.2 points in the Disabilities of the Arm, Shoulder and Hand score. Both groups showed a significant improvement in time response. CONCLUSIONS: This study demonstrates the beneficial effects of autologous proliferative therapies in the treatment of lateral epicondylitis. The data show that laser application and ACP therapy lead to a clinical improvement in epicondylopathia. Especially the new treatment with ACP can be highlighted as an alternative and as an easy-to-apply therapy option for clinical practice.

Biomechanical evaluation of meniscal root repair: a porcine study.

PURPOSE: Meniscal root repair is commonly practised using transtibial pull-out sutures. The purpose of the study was to investigate whether these are effective in restoring contact of the root to its footprint and a normal loading pattern of the cartilage under restricted loading conditions as used post-operatively. METHODS: First, a transtibial pull-out suture was simulated using porcine menisci (n = 10). It was repetitively loaded (100×; 1-10 N) and the elongation of the suture determined. In the second part of the study, porcine knees (n = 8) were subjected to repetitive low-level femoro-tibial loads (50 cycles; 100 N). A displacement sensor measured the deformation of the cartilage in the area of femoro-tibial contact. The residual deformation of the cartilage, which results from its viscoelastic behaviour, was determined as a measure of the local stress. Three scenarios were investigated: meniscal root intact, detached, and repaired. RESULTS: Repetitive loading caused a median suture elongation of 3.8 mm. Residual deformation of the cartilage was increased (p = 0.047) with the root detached. Root repair could not restore it to normal (n.s.). CONCLUSIONS: In this model, meniscus root repair was not effective in restoring the normal loading pattern of the cartilage because cyclic loading caused an elongation of the repair. CLINICAL RELEVANCE: In practice, this effect might impair the healing of repaired meniscal roots to the tibial bone.

Tensile forces on repaired medial meniscal root tears.

PURPOSE: The goals of this study were to measure the tensile forces acting on repaired medial meniscal root lesions and to investigate how they depend on femorotibial rotation, flexion, and compressive load. METHODS: In 6 human cadaveric knees, the posterior medial meniscal root was completely detached and then repaired with a pullout suture. A force transducer was installed such that it measured tensile forces acting on the suture. The resultant tension at the posterior medial meniscal root was measured for flexion angles up to 120° at 2 levels of femorotibial compressive load (100 and 500 N) in neutral, internal, and external rotation of the knee. RESULTS: Rotation had a highly significant effect on root tension (P < .001). Internal rotation of the femur increased the resultant tension, whereas external rotation decreased it. The tension at the meniscal root was related to the femorotibial load (P < .001). Although no significance was reached, a trend toward higher flexion angles causing more tension was observed. The highest mean tension of 60.1 ± 20.2 N was generated with internal rotation, a 500-N load, and 90° flexion. CONCLUSIONS: Our study shows in a human in vitro model that motion and weight loading of the knee can generate considerable tensile forces in the posterior medial meniscal root. Internal rotation of the femur increases the resultant tension substantially, whereas external rotation has the opposite effect. CLINICAL RELEVANCE: The data can potentially aid the surgeon in finding appropriate rehabilitation exercises after a medial meniscal root repair.

Anteroposterior and rotational stability in fixed and mobile bearing unicondylar knee arthroplasty: a cadaveric study using the robotic force sensor system.

PURPOSE: Different bearing designs in unicondylar knee arthroplasty (UKA) have been developed in order to influence the rate of polyethylene wear. Increased anteroposterior translation and rotation after UKA has been hypothesized due to changes in joint surface geometry. The mobile bearing design was expected to show increased anteroposterior translation compared to the fixed bearing and biconcave bearing design. METHODS: Six human cadaver knees were used for the tests. Anteroposterior and rotational knee stability was analysed in 0°, 30°, 60°, 90° and 120° of knee flexion using a robotic testing system (KR 125, KUKA Robots Augsburg, Germany). Three forces and moments were measured in a Cartesian coordinate system with a resolution of 1.0 N and 0.1 Nm. RESULTS: There was no difference between the native knees and the knees after UKA in AP translation and rotation in all knee flexion angles. The factor knee flexion angle had a significant impact on the anterior translation when the type of bearing was neglected (p ≤ 0.015). CONCLUSION: This study shows that the natural knee stability in AP translation and rotation can be preserved in UKA. The preserved knee stability in different planes after UKA underlines the advantage of UKA when surgery is required in osteoarthritic changes of the medial compartment.

No difference between tibia-first and femur-first techniques in TKA using computer-assisted surgery.

PURPOSE: The measured resection technique and the gap-balancing technique are two philosophies used in total knee surgery. It is still unknown whether one or the other technique provides superior results when computer-assisted surgery is performed. We hypothesized that the gap-balancing technique improves joint stability because the technique relies primarily on the soft tissue. METHODS: A prospective controlled study was performed in 116 patients using the tibia-first or femur-first technique. The Columbus(TM) total knee system and the Orthopilot(®) (Aesculap(®) AG, Tuttlingen, Germany) navigation system were used in all cases. Sixty-three patients were allocated to the femur-first technique (group F) and 53 patients to the tibial first technique (group T). The mean follow-up time was 11.4 ± 1.1 months. The KSS, KOOS and SF-36 were taken prior to surgery and at the time of follow-up for clinical assessment. Long-leg weight-bearing radiographs were performed to assess ligament alignment. Radiographs in varus and valgus stress were performed using the Telos(®)-Instrument (Telos(®) GmbH, Greisheim, Germany) under a force of 15 N at the time of follow-up for the assessment of medial-lateral stability. The nonparametric t test (Mann-Whitney U-test) was used in order to compare the ligament stability and the scores between group F and group T. RESULTS: The lateral joint space opening for groups F and T was 3.4° ± 1.4° and 3.9° ± 1.7°, respectively (n.s.), and the medial joint space opening for groups F and T was 4° ± 1.4° and 4.1° ± 1.7°, respectively (n.s.). The femorotibial mechanical axis for groups F and T revealed 1.4° ± 1.2° and 0.7° ± 2.0° of varus, respectively (p = 0.138). The clinical assessment showed significant improvement according to KSS, KOOS and SF-36 in all subscales. Neither of the sores showed significant differences between the two groups. CONCLUSION: The surgeon should use his/her preferred surgical technique providing the implantation is performed with computer assistance. It remains unclear whether the same findings will occur after conventional surgery. LEVEL OF EVIDENCE: II.

Local treatment of meniscal lesions with vascular endothelial growth factor.

BACKGROUND: The healing potential in the avascular regions of the meniscus is very limited, and improving the vascularity might be a reasonable way to improve healing. Vascular endothelial growth factor (VEGF) is one of the most potent proangiogenetic factors. We hypothesized that the local application of VEGF(165) would (1) improve the healing of a lesion in the avascular region of the meniscus, (2) induce angiogenesis in both the avascular and vascular regions, and (3) increase the amounts of VEGF mRNA and VEGF. METHODS: In eighteen sheep, the medial menisci were cut longitudinally in the avascular region and were sutured. Three groups were established depending on the suture material: (1) uncoated Ethibond, (2) Ethibond coated with VEGF(165) and its carrier Poly(D,L-Lactide) (PDLLA), and (3) Ethibond coated with PDLLA. The contralateral medial menisci served as a control group. Each of the three suture type groups included six animals. After eight weeks, the sheep were killed, and the menisci were examined macroscopically. Immunohistochemistry of Factor VIII and VEGF and real-time reverse-transcription polymerase chain reaction (RT-PCR) of VEGF mRNA were performed. Additionally, the VEGF release kinetics from the VEGF/PDLLA-coated suture were evaluated in vitro. RESULTS: In this model, VEGF did not improve meniscal healing. It did not increase angiogenesis in the avascular or vascular region, the VEGF concentration, or the amount of VEGF mRNA. VEGF release from the coated suture peaked on Day 3 and was nearly zero on Day 9. CONCLUSIONS: The local application of VEGF(165) as eluted from suture did not increase meniscal angiogenesis or improve meniscal healing. In addition, there was no effect on the amount of VEGF mRNA and VEGF. The VEGF carrier (PDLLA) may have been inadequate because of the short duration of VEGF supply.

The effect of a nonanatomic repair of the meniscal horn attachment on meniscal tension: a biomechanical study.

PURPOSE: The purpose of this biomechanical study was to investigate the potential effect of a nonanatomic repair of the meniscal horn attachment on the resultant circumferential tension in a large animal model and to show that the circumferential tension of the meniscus affects the local stress of the cartilage. METHODS: All investigations were done in the medial compartment of porcine knees. First, the anterior horn attachment of the meniscus was mechanically separated from the surrounding tibial bone and fitted with a force transducer (n = 8). The femorotibial joint was loaded in compression at different flexion angles, and the resultant tension at the horn attachment was recorded. The measurements were done with the horn attachment at its anatomic position and repeated with the horn attachment being displaced medially or laterally by 3 mm. In the second part the local deformation of the cartilage under a femorotibial compressive load was measured at different levels of meniscal hoop tension (n = 5). RESULTS: A nonanatomic position of the horn attachment had a significant effect on the resultant tension (P < .01). Placing the horn attachment 3 mm medially decreased the tension at the horn attachment by 49% to 73%, depending on flexion angle and femorotibial load. The opposite placement resulted in a relative increase in the tension by 28% to 68%. Lower levels of meniscal hoop tension caused increased deformation of the cartilage (P < .05), indicating increased local stress. CONCLUSIONS: A nonanatomic position of the horn attachment strongly affects conversion of femorotibial loads into circumferential tension. There is a narrow window for a functionally sufficient repair of meniscal root tears. CLINICAL RELEVANCE: Although clinical inferences are limited because the specimens used were from a different species, there seems to be only a narrow window for a mechanically sufficient repair of root tears.

Meniscal repair.

The meniscus plays an important role in preventing osteoarthritis of the knee. Repair of a meniscal lesion should be strongly considered if the tear is peripheral and longitudinal, with concurrent anterior cruciate ligament reconstruction, and in younger patients. The probability of healing is decreased in complex or degenerative tears, central tears, and tears in unstable knees. Age or extension of the tear into the avascular area are not exclusion criteria. Numerous repair techniques are available, and suture repair seems to provide superior biomechanical stability. However, the clinical success rate does not correlate well with the mechanical strength of the repair technique. Biologic factors might be of greater importance to the success of meniscal repair than the surgical technique. Therefore, the decision on the most appropriate repair technique should not rely on biomechanical parameters alone. Contemporary all-inside repair systems have decreased the operating time and the level of surgical skill required. Despite the ease of use, there is a potential for complications because of the close proximity of vessels, nerves, and tendons, of which the surgeon should be aware. There is no clear consensus on postoperative rehabilitation. Weight bearing in extension would most likely not be crucial in typical longitudinal lesions. However, higher degrees of flexion, particularly with weight bearing, give rise to large excursions of the menisci and to shear motions, and should therefore be advised carefully. Long-term studies show a decline in success rates with time. Further studies are needed to clarify the factors relevant to the healing of the menisci. Tissue engineering techniques to enhance the healing in situ are promising but have not yet evolved to a practicable level.

Tensile forces at the porcine anterior meniscal horn attachment.

Tibiofemoral compression causes circumferential tension in the knee meniscus, which is transferred to the tibial bone at the anterior and posterior attachments. The objective of the study was to measure the resulting tensile forces at the horn attachment in a porcine model. The anterior horn attachment of the porcine medial meniscus (n = 10) was separated from the surrounding bone with a core reamer. A force transducer was installed such that tensile forces acting upon the now mobile horn attachment could be measured. The tibiofemoral joint was loaded in compression, starting at a preload of 30 N, with three 150-N increments, giving 180, 330, and 480 N load. Flexion angles of 0, 30, and 60 degrees were investigated. The average resultant tension at the horn attachment was 26.3, 40.6, and 55.4 N with full extension, 29.2, 47.8, and 62.2 N at 30 degrees flexion and 30.1, 49.6, and 68.1 N at 60 degrees flexion. The tibiofemoral compression had a significant effect on the tension (p < 0.001), whereas no influence of the flexion angle was found (p = 0.291). The study demonstrates that tibiofemoral compressive loads cause considerable tensile forces at the anterior meniscal horn attachment. The data are of interest for models of the repair or replacement of the knee menisci.

The effect of locally applied vascular endothelial growth factor on meniscus healing: gross and histological findings.

INTRODUCTION: Tears in the peripheral part of the menisci have a better healing potential than tears in the central part, because the central two-thirds of the menisci are avascular. We hypothesized that healing of meniscus tears in the avascular zone can be promoted by the local application of the angiogenic factor vascular endothelial growth factor (VEGF). MATERIALS AND METHODS: A tear was created in the avascular zone of the medial meniscus in 18 merino sheep. The tear was then repaired with an uncoated suture (group 1), a suture coated with PDLLA (group 2), and by a suture coated with PDLLA/VEGF (group 3). RESULTS: After 6 weeks, we observed increased immunostaining for factor VIII in the VEGF-treated group 3. However, in this treatment group no meniscus healed completely. In the uncoated suture group and in the PDLLA-coated-suture group, partial healing was observed in three animals and complete healing in three animals, respectively. CONCLUSION: In this experiment the local application of VEGF via PDLLA-coated sutures did not promote meniscus healing. Growth factors might not always be a promising tool for tissue repair.

Distraction forces on repaired bucket-handle lesions in the medial meniscus.

BACKGROUND: Numerous studies have investigated the biomechanical properties of meniscal repair techniques. One of the most commonly discussed parameters is the failure load in the axis of insertion, although little is known about the distraction forces actually occurring at repaired bucket-handle lesions. HYPOTHESIS: There are clinically relevant distraction forces on repaired meniscus bucket-handle lesions. STUDY DESIGN: Controlled laboratory study. METHODS: Meniscus bucket-handle lesions were created and repaired in human cadaveric knees with a vertical suture made from a braided steel wire. A small-sized load sensor was connected to the wire at the periphery of the meniscus. The distraction forces acting on the lesion were measured at different knee joint angles (0 degrees -120 degrees of flexion) with internal and external rotation and with and without weight loading. Forces in excess of 10 N were considered to have clinical relevance. RESULTS: Mean forces on the meniscus repair ranged from 1.64 to 4.72 N. Irrespective of the modalities (ie, different flexion angles, weight load, direction of rotation), it was found that the forces were well below the cutoff value of 10 N (P < .01). Increasing flexion angles generally did not cause an increase in distraction forces. CONCLUSION: The data suggest that distraction forces are not the primary factor in the mechanical stability of meniscal repair. It must therefore be assumed that other factors such as shear forces are of greater significance. CLINICAL RELEVANCE: The results may help to validate the biomechanical properties of different meniscal repair techniques.

Locally applied angiogenic factors--a new therapeutic tool for meniscal repair.

Tears in the peripheral part of the menisci have a better healing potential than tears in the central part, because the central two-thirds of the menisci are avascular. The avascular status of the meniscus is maintained by the expression of antiangiogenic factors such as endostatin. The distribution of endostatin in the menisci correlates with the degree of vascularization. Endostatin immunostaining is strong in the avascular zone and reduced in the vascularized outer one-third. Endostatin interacts with signal transduction of the vascular endothelial growth factor (VEGF) by reducing VEGF-induced kinase (Erk1/2) phosphorylation. VEGF plays an important role in angiogenesis in fetal menisci and it is down-regulated in the adult meniscus. We hypothesized that healing of meniscal tears in the avascular zone can be promoted by the local application of the angiogenic factor VEGF. To evaluate this hypothesis a tear was created in the avascular zone of the medial meniscus in 18 merino sheep. The tear was then repaired with an uncoated suture (group 1), a suture coated with PDLLA (group 2), and by a suture coated with PDLLA/VEGF (group 3). After 6 weeks we observed increased factor VIII immunostaining in the VEGF-treated group. However, in this treatment group (VEGF/PDLLA) no meniscus healed. In the uncoated suture group and in the PDLLA-coated suture group partial healing was observed in three animals and complete healing in three animals, respectively. Factor VIII expression is normally restricted to vascular endothelial cells. In this study, however, single endothelial cells could be detected in the menisci of the VEGF/PDLLA group. This finding suggests that the application of VEGF might have stimulated proliferation of vascular endothelial cells but the application of VEGF was not successful in stimulating the more complex process of vasculogenesis. Further immunohistochemical examinations of the specimen have shown that in the VEGF/PDLLA group there is strong immunostaining against matrix metalloproteinase 13 (MMP-13). In vitro studies have shown that VEGF can stimulate chondrocytes to proliferate but also to express MMP-13 via HIF1-alpha induction. Since meniscal fibrochondrocytes express the VEGF receptor 2 (KDR) the induction of MMP expression might be another factor which inhibits healing despite increased angiogenesis. In conclusion, the local application of VEGF via PDLLA-coated sutures does not promote meniscal healing. A single growth factor might not always be a promising tool for the promotion of tissue repair. Further studies have to find out if growth factor combinations (VEGF and angiopoitin) might be more effective in stimulating vasculogenesis during meniscal healing.