Differences in cellular properties and responses to growth factors between human ACL and MCL cells

The anterior cruciate ligament (ACL) has poor healing responses compared with those of the medial collateral ligament (MCL). It has been implied that this is partially due to the poor reparative capacity of ACL cells for ligament injury. The present study was designed to elucidate the reparative capacities of human ACL and MCL cells by investigating their cellular properties and their responses to growth factors. Human ACL and MCL were obtained from seven fresh human cadavers. The cells were isolated from each tissue, and primary cultures were used for the examination. The growth rates of all the human ACL cells were lower than those of the human MCL cells; consistent with this, the doubling time of the ACL cells was 30 ± 7.4% longer than that of the MCL cells. The chemotactic migration of human ACL cells was 33 ± 8.1% slower and the synthesis of DNA and collagen in human ACL cells was 29 ± 6.3% and 31 ± 9.7% lower, respectively, in comparison with those of MCL cells. Cellular responses, in terms of DNA synthesis, in human ACL cells to either basic-fibroblast growth factor (1.0 and 10.0 ng/ml) or transforming growth factor-β (1.0 ng/ml) were lower than those of human MCL cells. However, no differences in the cellular responses in terms of collagen synthesis were found. Composite data show that human ACL cells have poorer cellular properties and lower responses to growth factors compared with those of human MCL cells, which suggests that the reparative capacity of human ACL cells may be poorer than that of human MCL cells. Received for publication on Sept. 2, 1998; accepted on Jan. 29, 1999     

Type I procollagen gene expression in normal and early healing of the medial collateral and anterior cruciate ligaments in rabbits: an in situ hybridization study

The purpose of this study was to compare the levels of procollagen type I messenger RNA (mRNA) in normal and healing medial collateral ligament (MCL) and anterior cruciate ligament (ACL) in a rabbit model. Our method of injury involved a surgical model with identical partial lacerations in the midsubstance of the MCL and ACL. Paraffin sections of normal ligaments, and ligaments 3, 7, 14, and 28 days postlaceration were studied by in situ hybridization to compare and follow the level of type I procollagen mRNA in the two ligaments. A complementary DNA (cDNA) probe corresponding to alpha 1(I) procollagen mRNA was labeled with [32P]d-CTP. After hybridization, autoradiography, and staining of the sections, the level of procollagen mRNA was assessed by microscopic examination. A higher level of procollagen mRNA was consistently detected in normal MCL than in normal ACL, suggesting higher collagen synthetic activity in the MCL. At the injury sites of the MCL and ACL, the levels of type I procollagen mRNA increased at all post-laceration periods, reaching its highest level at 14 days postsurgery. The MCL healing site had a considerably higher level of procollagen mRNA than the ACL healing site (i.e., injury site) at all postoperative intervals. The results demonstrate that procollagen mRNA levels in MCL tissue are higher than those in ACL tissue under normal conditions, as well as in response to injury. The differences in the procollagen mRNA levels of MCL and ACL may reflect the synthesis of collagen in these tissues, and may contribute to the differences in their healing capacities.     

Vascular physiology and long-term healing of partial ligament tears.

Functional outcomes of anterior cruciate ligament (ACL) injury are generally poorer than those of medial collateral ligament (MCL) tears. Following ligament damage, all phases of ligament healing require an adequate blood supply. We hypothesized that the differences in healing properties of the ACL and MCL would reflect their vascular responses to joint injury. This paper examines the long-term changes in blood flow and vascular volume of rabbit knee ligaments after direct injury, and under conditions of chronic joint instability induced by section of the posterior cruciate ligament (PCL). Standardized injuries were surgically induced in adult rabbit knee ligaments: partial MCL transection, partial ACL transection, or complete PCL transection (joint instability). Sixteen weeks later the blood flow and vascular volume of the ACL and MCL were measured and compared to control and sham-operated animals. Direct ligament injury induced significant increases in standardized blood flow and vascular volume of both ACL and MCL after 16 weeks; however, the vascular volume of the ACL was not higher than the control levels in the MCL. We conclude that direct injury to both the anterior cruciate and MCLs induces long-term physiological responses. Joint laxity is a common sequel to PCL injury. Chronic joint laxity failed to induce adaptive vascular responses in the ACL, while the MCL shows significant amplification of blood supply. Although both MCL and ACL showed increased weight after PCL transection, the lack of a long-term vascular response in the ACL may be a major factor in its the diminished healing potential.     

Selection of cell source for ligament tissue engineering

Use of appropriate types of cells could potentially improve the functionality and structure of tissue engineered constructs, but little is known about the optimal cell source for ligament tissue engineering. The object of this study was to determine the optimal cell source for anterior cruciate ligament (ACL) tissue engineering. Fibroblasts isolated from anterior cruciate ligament, medial collateral ligament (MCL), as well as bone marrow mesenchymal stem cells (MSC) were compared using the following parameters: proliferation rate, collagen excretion, expression of collagen type I, II, and III, as well as alpha-smooth muscle actin. Green fluorescent protein (GFP) transfected MSCs were used to trace their fate in the knee joints. MSC, ACL, and MCL fibroblasts were all highly stained with antibodies for collagen types I and III and alpha-smooth muscle actin while negatively stained with collagen type II. Proliferation rate and collagen excretion of MSCs were higher than ACL and MCL fibroblasts (p < 0.05), and MSCs could survive for at least 6 weeks in knee joints. In summary, MSC is potentially a better cell source than ACL and MCL fibroblasts for anterior cruciate ligament tissue engineering.     

Medial collateral knee ligament healing: Combined medial collateral and anterior cruciate ligament injuries studied in rabbits

We examined the histological appearance and biochemical properties of the healing medial collateral ligament (MCL) of a rabbit knee after combined MCL and anterior cruciate ligament (ACL) injury treated with ACL reconstruction and with or without MCL repair. By so doing, we hoped to understand better our previous biomechanical observations (Ohno et al. 1995) and possibly learn where to focus future investigation into improving the quality of the healing MCL.

Ligaments were examined at 6 and 12 weeks of healing. We found healing of all ligaments with hypercellularity and fibroblast elongation along the axis of loading, as expected. Unexpected, however, was the finding of multiple osteophytes in both the repaired and nonrepaired specimens at the medial borders of the joint and at the MCL insertions. These were felt to affect possibly the biomechanics of the MCL by causing stress risers at the point where they undermine the ligament. Biochemically, we demonstrated a correlation between collagen content and hydroxypyridinium crosslinks and modulus of elasticity. While this implies that the modulus is dependent on collagen content and hydroxypyridinium crosslink density, modulus is also probably dependent on other factors such as collagen organization, type and internal structure. Overall, the detailed characterization and correlation between the histological, biochemical, and biomechanical properties of the healing MCL in the severe knee injury model provide insight into the functional behavior of the healing MCL.     

Vascular structure and function in the medial collateral ligament of anterior cruciate ligament transected rabbit knees

To determine if decreased vascular responsiveness in the medial collateral ligament (MCL) of anterior cruciate ligament transected (ACL‐t) rabbit knees is due to pericyte deficiency associated with angiogenesis. Vascular responses to potassium chloride (KCl), phenylephrine, acetylcholine, and sodium nitroprusside (SNP) were evaluated in ACL‐t rabbit knees (n = 6) and control knees (n = 5) using laser speckle perfusion imaging. Ligament degeneration was determined by ultrasound imaging. Vascular and pericyte volume were measured using quantitative immunohistochemical volumetric analysis using CD31 and α‐smooth muscle actin antibodies with co‐localization analysis. Perfusion was increased in the ACL‐t rabbits 2.5‐fold. Responsiveness to phenylephrine, SNP, and acetylcholine was significantly decreased in the ACL knee while no change in KCl responses was seen. MCL ultrasound imaging revealed decreased collagen organization, increased ligament thickness, and increased water content in the ACL‐t MCL. Vascular Volume was increased fourfold in ACL deficient knees, while pericyte volume to endothelial volume was not changed. No difference in CD31 and α‐SMA co‐localization was found. Blood vessels in the MCL of ACL‐t knees do not lack smooth muscle. The MCL vasculature can undergo constrictive response to KCl, but have impaired receptor mediated responses and impaired nitric oxide signaling. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1104–1110, 2014.     

Bilogic characteristics of fibroblast cells cultured from the knee ligaments

OBJECTIVE: To culture fibroblast cells from the knee ligaments and to study the biological characteristics of these cells. METHODS: Cells of the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL) from New Zealand white rabbit were cultured in vitro. Cellular growth and expression of the collagen were analyzed. Moreover, an in vitro wound closure model was established and the healing of the ACL and the MCL cells was compared. RESULTS: Maximal growth for all these cells were obtained with Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum, but RPMI 1640 and Ham's F12 media were not suitable to maintain these cells. Morphology of both ACL and MCL cells from New Zealand white rabbit was alike in vitro, but the MCL cells grew faster than the ACL cells. Both cell types produced similar amount of collagen in culture, but the ratio of collage type I to type III produced by ACL cells was higher than that produced by MCL cells. Wound closure assay showed that at 36 hours after injury, cell-free zones created in the ACL cultures were occupied partially by the ACL cells; in contrast, the wounded zone in the MCL cultures was almost completely covered by the cells. CONCLUSIONS: Although the ACL cells and the MCL cells from New Zealand white rabbit show similar appearance in morphology in culture, the cellular growth and the biochemical synthesis of collagen as well as the healing in vitro were significantly different. These differences in intrinsic properties of the two types of cells in vitro might contribute to the differential healing potentials of these ligaments in vivo.     

GDF‐5/7 and bFGF activate integrin α2‐mediated cellular migration in rabbit ligament fibroblasts

Cellular activities responding to growth factors are important in ligament healing. The anterior cruciate ligament (ACL) has poor healing potential compared to the medial collateral ligament (MCL). To assess the differences, we investigated the proliferation, migration, adhesion, and matrix synthesis responding to growth factors in rabbit ACL and MCL fibroblasts. ACL cell proliferation to basic fibroblast growth factor (bFGF), bone morphogenetic protein‐2, growth and differentiation factor (GDF)‐5, and GDF‐7 treatment was similar to that of MCL cells. GDF‐5 enhanced Col1a1 expression in ACL and MCL fibroblasts up to 4.7‐ and 17‐fold levels of control, respectively. MCL fibroblasts showed stronger migration activities in response to bFGF and GDF‐5 than ACL cells. GDF‐5/7 and bFGF also changed the stress fiber formation and cellular adhesion by modulating the distribution of integrin α2. Functional blocking analyses using anti‐integrin α2 antibodies revealed that cellular migration responding to growth factors depended on the integrin α2‐mediated adhesion on type I collagen. The expression of integrin α2 was also increased by growth factors in both cells. Our results demonstrate that GDF‐5/7 and bFGF stimulate cellular migration by modulating integrin α2 expression and integrin α2‐dependent adhesion, especially in MCL fibroblasts. These findings suggest that the different healing potential between ACL and MCL may be caused by different cellular behavior in the integrin α2‐mediated cellular migration in response to growth factors. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:225–231, 2010     

Effect of tibial attachment location on the healing of the anterior cruciate ligament freeze model

We studied the healing response of a devitalized anterior cruciate ligament to a treatment of initial anterior-posterior joint translation in goats. Devitalization and devascularization were achieved by five successive freeze-thaw cycles. Anterior-posterior translation was surgically altered by an osteotomy of the tibial attachment of the devitalized ligament and its reattachment either in the anatomical position or in a position 5 mm posterior. Six weeks after the first surgery, the same procedure was performed on the contralateral limb, except that the ligament was reattached in the alternate position. Six months after the initial surgery, femur-anterior cruciate ligament-tibia specimens were tested to determine their structural and mechanical material properties. Anatomic ligament placement resulted in reduced anterior-posterior translation (p < 0.05) and greater anterior joint stiffness (p < 0.05). Maximum load (p < 0.05) and ligament stiffness (p < 0.01) also were greater for the anatomically placed anterior cruciate ligaments. The maximum load for anatomically placed ligaments averaged 1.625 ± 211 N (SEM). The strength of the posteriorly placed anterior cruciate ligament, 895 ± 164 N. was similar to results of historical anterior cruciate autograft reconstructions. Ligament failure occurred near the tibial insertion in the posteriorly placed ligaments more often than in the anatomically placed ligaments (four of five times compared with one of five times). Ligament failure near the tibial insertion occurred with lower mean maximum load than failure at the midsubstance or by bone avulsion (796 compared with 1.592 N: p < 0.05). These data support the hypothesis that ligament laxity is important to the healing and remodeling of anterior cruciate ligament grafts.     

Differential expressions of lysyl oxidase family in ACL and MCL fibroblasts after mechanical injury

Lysyl oxidase (LOX) family has the capacity to catalyse the cross-linking of collagen and elastin, implicating its important fundamental roles in tissue development and injury healing. However, the variations in expression of the LOX family in the normal and injured anterior cruciate ligament (ACL) are not fully known. To better understand the role of LOX family in the self-healing inability mechanism of injured ACL, this study is to measure the LOX family's differential expressions in ACL and medial collateral ligament (MCL) fibroblasts after mechanical injury induced by using an equi-biaxial stretching chamber. The cells received various degrees of mechanical stretch 0% (resting state), 6% (physiological state) and 12% (injurious state), respectively. The gene profile and protein expressions were analysed by semi-quantitative PCR, quantitative real-time PCR and Western blotting. At physiological state, gene expression showed LOX in ACL was 2.6–5.2 folds higher than that in MCL in all culture time periods, LOXL-4 1.2–3.6 folds, but LOXL-3 in MCL showed 1.1–4.8 folds higher than that in ACL. In injurious state, MCL gene expressions were 2.8–29.6 folds higher than ACL in LOX, LOXL-2, LOXL-3 and LOXL-4 at 2, 6 and 12 h periods. These differential expression profiles of the LOX family in the two ligament tissues were further used to explain the intrinsic differences between ACL and MCL, and why injured ACL could not be amenable to repair itself, whereas MCL could.     

Healing of the medial collateral ligament following a triad injury: a biomechanical and histological study of the knee in rabbits.

The effect of a partial medial meniscectomy and anterior cruciate ligament (ACL) transection on medial collateral ligament (MCL) healing was studied in skeletally mature rabbits. Two groups of animals, group I (isolated MCL rupture) and group II (MCL rupture with ACL transection and partial medial meniscectomy), were examined. At 6 and 12 weeks postoperatively, histological examination of the healing MCL and biomechanical evaluation of the varus-valgus (V-V) knee rotation and tensile properties of the femur-MCL-tibia complex (FMTC) were performed. Group II animals experienced substantial joint degeneration by 6 weeks. Progressive osteophyte formation was observed adjacent to the MCL insertions along with proximal migration of the MCL tibial insertion between 6 and 12 weeks. Histologic examination of the healing MCL substance from both groups showed disorganized collagen, inflammation, and fibroblast proliferation that decreased over time. For group II knees, the V-V knee rotation was found to be significantly elevated (4.7 to 5.2 times the contralateral control), and did not decrease with time. In contrast, the V-V knee rotations of the group I specimens were 1.8 times greater than control immediately following injury, and approached control values by 12 weeks. Tensile testing of the FMTCs revealed that the ultimate load increased with time for both groups, but group I had significantly higher values than group II. The linear stiffness in group I was not different than that group II and did not increase with time. For the mechanical (material) properties of the healed MCL substance, the modulus of the healing tissue for group II was only 40% that of group I. The structural properties of the FMTC and the mechanical properties of the MCL substance from both groups at 6 and 12 weeks were significantly different from the contralateral controls. We further demonstrated that immediately after ACL reconstruction, the V-V rotation of group II knees could be restored to group I levels. Recent clinical studies of MCL healing following isolated complete ligament tears have suggested that nonoperative management without immobilization leads to excellent treatment outcome. However, in more severe injuries involving additional tissues, poor quality of the healed ligament tissue and articular degeneration are observed. Our results demonstrate the deleterious effects of an untreated triad injury on the healing of the MCL substance and its insertions. Examination of the MCL substance suggests that a much larger healing mass is formed following a triad injury, which partially compensates for inferior ligament mechanical properties.(ABSTRACT TRUNCATED AT 400 WORDS)     

Correlation of healing capacity with vascular response in the anterior cruciate and medial collateral ligaments of the rabbit.

In clinical terms, functional recovery after anterior cruciate ligament (ACL) injury is generally poorer than after medial collateral ligament (MCL) injury. In experimental studies of injury, the early phases of ligament healing require an augmented blood supply. We hypothesized that the differences in healing properties of the ACL and MCL would be reflected in the magnitude of their vascular responses to partial injury. This study is the first to quantify and define the time course of changes in blood flow and vascular volume following hemisection of the rabbit ACL and MCL.Adult female rabbits were assigned to control, sham operation, ACL hemisection or MCL hemisection groups. Standardized ACL or MCL injuries were surgically induced. About 2, 6 or 16 weeks later, blood flow and vascular volume of the ACL and MCL were measured.The MCL of the rabbit responded to hemisection with a large significant increase in blood flow and a substantial angiogenic response associated with inflammation and scar formation. During subsequent matrix remodelling, blood flow and vascular volume returned towards control values. In contrast, the ACL showed only a 2-fold increase in vascular volume, no increase in blood flow and atrophied after hemisection. The superior capacity of the MCL to increase its blood supply through angiogenesis and increased flow is essential for ligament healing to occur, and may be the major difference in healing potential between the ACL and MCL.     

保留残迹对前交叉韧带重建移植物愈合影响的组织学研究

[目的]观察保留残迹对前交叉韧带(anterior cruciate ligament,ACL)重建移植物愈合的影响,并探讨其原因.[方法]新西兰兔30只(封闭群,体重2.9～3.5 kg,平均3.2 kg)随机分为3组,每组10只.取其跟腱为移植物,切断双侧前交叉韧带,随机一侧保留ACL残迹,对侧切除残迹,行前交叉韧带重建.分别于术后4、8、12周处死动物,取关节内重建ACL移植物标本10%多聚甲醛固定、10%EDTA脱钙、包埋、切片,HE染色及Masson、PAS特殊组织化学染色,检测成纤维细胞密度及观察组织学形态,数据采用SPSS 12.0软件进行统计分析.[结果]各时间段保留残迹组移植物HE染色组织切片成纤维细胞密度均高于切除残迹组,两组比较有显著统计学差异(P<0.05),两处理组8周时细胞密度高于4、12周,不同时间段比较有统计学差异(P<0.05).各时间段保留残迹组移植物的组织学表现均优于切除残迹组.[结论]保留残迹ACL重建有利于新生细胞长入替代移植物,促进移植物组织结构成熟.     

Ultrastructural differences between the cells of the medical collateral and the anterior cruciate ligaments

The anterior cruciate ligament (ACL) does not heal after an interstitial tear, in contrast to the medial collateral ligament (MCL), whose interstitial tears heal readily. The light microscopic and ultrastructural differences between the cells of the two ligaments were studied in rabbit knees to observe the healing characteristics of the two ligaments. A rabbit knee was chosen because the rabbit ACL, like that of humans, does not heal following interstitial injury. The cells populating the MCL have the characteristics of fibroblasts. The cells of the ACL resemble fibrocartilage cells. The phenotypic differences in the cells of the two ligaments may be important determinants of the differences in healing.     

Characterization of the intrinsic properties of the anterior cruciate and medial collateral ligament cells: an in vitro cell culture study.

The poor healing abilities of the anterior cruciate ligament (ACL) in contrast to those of the medial collateral ligament (MCL) are well known. Different intrinsic properties of the constituent cells of these ligaments have been proposed to be one of the factors in the differential repair mechanisms. To examine this hypothesis, we have established primary cell lines of ACL and MCL from the tissue explants of approximately similar dimensions and have studied their behavior in vitro. The outgrowth of cells from ACL explants was slower than from MCL explants, as shown by the size of the surrounding clusters of cells. Both ACL and MCL cultures exhibited typical fibroblastic morphology. No significant differences were observed in either attachment or growth of cells from the attached explants derived from various segments of ACL and MCL. Growth curves of ACL and MCL cultures at both passage numbers 2 and 6 showed a slower rate of proliferation of ACL cells than MCL cells (p less than 0.005). DNA synthesis measured in terms of [3H]thymidine incorporation (CPM/10(3) cells) of both log phase (ACL = 607.5 +/- 5.4 vs. MCL = 1356.4 +/- 11.3) and confluent (ACL = 83.0 +/- 3.6 vs. MCL = 189.8 +/- 5.4) cultures, supports the conclusion that differential proliferation rates of these cells exist in culture. FITC-phalloidin staining (for actin) of later passage cultures (P3-P5) showed a spread-out appearance of ACL cells and an elongated appearance of MCL cells. Relatively more stress fibers were seen within ACL cells. SDS-PAGE and Western blot analysis of cellular proteins revealed higher actin (43 kDa) content in ACL cells than in MCL cells. In vitro wound closure assay was performed by creating a uniform wound of 0.6 mm width in the confluent layer of ACL and MCL cultures. By 48 h postwounding, cell-free zones created in ACL cultures were occupied partially by single cells in a nonconfluent fashion. In contrast, the wounded zone in the MCL cultures was almost completely covered by the cells. Results presented in this report demonstrate a lower proliferation and migration potential of ACL cells in comparison with MCL cells. These differences in intrinsic properties of ACL and MCL cells that were observed in vitro might contribute to the differential healing potentials of these ligaments in vivo.     

Immunohistochemical localization of beta 1-integrins in anterior cruciate and medial collateral ligaments of human and rabbit.

The integrins are a family of adhesion-mediating cell surface receptors that play critical roles in cell-extracellular matrix interactions and have been shown to be important in the healing response in several tissues. We have studied integrin expression in normal human and rabbit anterior cruciate (ACL) and medial collateral (MCL) ligaments of the knee as a preamble to studies of beta 1-integrin expression in healing ligaments. Histologic sections of human and rabbit ACL and MCL were probed for integrin expression utilizing integrin-specific monoclonal antibodies (mAbs) followed by immunoperoxidase detection. Staining of human specimens with mAbs revealed the presence of beta 1-, alpha 1-, and alpha 5-integrin chains on the tissue fibroblasts of both ACL and MCL, while staining of rabbit specimens with rabbit integrin-reactive monoclonals revealed the presence of beta 1- and alpha 5-integrin on these ligaments. Equivalent amounts of the integrins studied were present on normal ACL and MCL. We conclude that the rabbit is an appropriate model for analyzing the expression and functional role of integrins in ligament wound healing.     

Effect of cyclic strain and plating matrix on cell proliferation and integrin expression by ligament fibroblasts.

The role of cell surface integrins in cell migration, proliferation, and attachment to matrix molecules is well known. Integrin-matrix interactions have been implicated in mechanotransduction and load transmission from the outside to the inside of the cell. In this study, the effect of cyclic strain on the cell proliferation, attachment, and expression of integrin subunits beta1, beta3, and alpha5 was determined in anterior cruciate ligament (ACL) and medial collateral ligament (MCL) fibroblasts grown on polystyrene, Type I collagen, laminin, elastin, and fibronectin. ACL fibroblast proliferation was not affected by growth substrate whereas MCL cells reached confluence more rapidly on fibronectin compared with collagen or polystyrene. Exposure to 5% cyclic strain resulted in a significant decrease in ACL and MCL fibroblast proliferation on fibronectin and Type I collagen. MCL cells showed a greater strain-dependent inhibition of cells grown on a fibronectin substrate than those grown on collagen. This matrix-dependent effect of strain on cell proliferation was not seen with ACL cells. Attachment of ACL and MCL fibroblasts was stronger to fibronectin compared with Type I collagen, laminin, and polystyrene. In the absence of applied load, the expression of beta1, beta3, and alpha5 subunits was not substrate dependent and the expression of beta1 and alpha5 integrin subunits was higher in MCL cells than ACL cells on all substrates. In contrast, the expression of beta3 integrin subunit was higher in ACL cells than MCL cells. In response to 5% strain, beta1, and alpha5 expression increased in all fibroblasts with MCL cells having a higher magnitude of expression. beta3 expression showed a 90% increase in response to load when grown on laminin for both MCL and ACL fibroblasts and demonstrated no change in expression on Type I collagen or fibronectin. The duration of applied strain from 2 versus 22 h had no effect on cell proliferation or integrin expression.     

Healing and repair of ligament injuries in the knee

Although methods of treating ligamentous injuries have continually improved, many questions remain about enhancing the rate, quality, and completeness of ligament healing. It is known that the ability of a torn ligament to heal depends on a variety of factors, including anatomic location, presence of associated injuries, and selected treatment modality. A grade III injury of the medial collateral ligament (MCL) of the knee usually heals spontaneously. Surgical repair followed by immobilization of an isolated MCL tear does not enhance the healing process. In contrast, tears of the anterior cruciate ligament (ACL) and the posterior cruciate ligament often require surgical reconstruction. The MCL component of a combined ACL-MCL injury has a worse prognosis than an isolated MCL injury. The results of animal studies suggest that nonoperative treatment of an MCL injury is effective if combined with operative reconstruction of the ACL. Experimentation using animal models has helped to define the effects of ligament location, associated injuries, intrinsic factors, surgical repair, reconstruction, and exercise on ligament healing. New techniques utilizing growth factors and cell and gene therapies may offer the potential to enhance the rate and quality of healing of ligaments of the knee, as well as other ligaments in the body.     

The central ACL defect as a model for failure of intra-articular healing.

Intra-articular soft tissues, such as the anterior cruciate ligament (ACL), fail to heal in contrast to the extra-articular medial collateral ligament (MCL), which undergoes classic healing. The goal of this study was to validate a model for failure of intra-articular healing that could be used in the future to test new repair strategies. We conducted a two-part experiment, the first part ex vivo, and the second in vivo. Our initial ex vivo experiments were used to determine the optimal width of the central defect in the canine ACL that would produce reproducible structural properties at time zero. The second experimental series used this optimal scalpel blade width to create a central defect in the canine ACL followed by measurement of structural properties in the ACL after either a 3- or 6-week in vivo healing period. A 3.5-mm beaver blade resulted in a maximum tolerated load of 56.8 +/- 4.7% (mean +/- SEM) of control at time zero. After the 3- and 6-week in vivo healing periods, the maximum load was 74.6 +/- 5.3 at 3 weeks and 64.9 +/- 3.8% at 6 weeks compared to control. Thus, biomechanical parameters tested at 6 weeks after creation of a defect showed no significant gains from defects tested immediately after the creation of injury. The centrally placed ACL defect in this canine model demonstrates failure to mechanically heal, which should prove suitable for future in vivo evaluation of the biomechanical and histological response to tissue engineering repair strategies for intra-articular soft tissues.     

分期修复重建膝关节多发韧带损伤的临床疗效

目的 :探讨关节镜下分期治疗膝关节多发韧带损伤的临床疗效。方法 :2006年3月至2012年6月,关节镜下分期治疗膝关节多发韧带损伤14例(14膝)。男8例,女6例;年龄20~49岁,平均(31.8±8.1)岁。患者均行X线、MR检查,提示10例前交叉韧带、后交叉韧带及内侧副韧带损伤,4例前交叉韧带、后交叉韧带及后外侧角损伤。合并内侧半月板损伤4例,外侧半月板损伤2例。Ⅰ期手术治疗内侧副韧带损伤、后交叉韧带及半月板,术后固定3周后开始主被动功能锻炼,3~6个月后膝关节活动范围正常且存在明显松弛时Ⅱ期重建前交叉韧带和(或)后交叉韧带。结果:术后切口均Ⅰ期愈合,无感染等手术相关并发症发生。患者均获随访,时间24~80个月,平均48.9个月。末次随访时膝关节Lysholm评分达87.1±2.8,优于术前19.6±0.9(t=12.3,P0.01)。国际膝关节评分委员会(International Knee Documentation Committee,IKDC)评级:9例接近正常,5例异常。结论 :关节镜下分期治疗膝关节多发韧带损伤能有效恢复膝关节稳定性和功能。