Mechanoreceptors in collateral knee ligaments: an animal experiment.
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The mechanoreceptors in the collateral ligaments of the knee joint in rat hindlimbs were studied. In group II (n=10) the femoral and obturator nerves were sectioned. In both groups III and V (n=20) the sciatic nerve was sectioned. In group V (n=10) the sectioned sciatic nerve was sutured 4 weeks after sectioning. In group IV (n=10) all three nerves were sectioned. Group I (n=10) served as control. After 4 months all animals were killed. The ligaments of the knee joint were preserved and stained with gold chloride, paraffin-embedded and cut in sagittal serial sections. The results showed that 4 months after partial or total denervation of the limb, there was necrosis and a decrease in the number of mechanoreceptors, which was dependent upon the severity and site of the lesion. After suture of the sciatic nerve the increase in mechanoreceptors suggested a regenerative process. (+info)
Collagen fibril diameter distributions in rabbit anterior cruciate and medial collateral ligaments: changes with maturation.
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This study presents morphometric analyses of the collagen fibril diameters of rabbit anterior cruciate and medial collateral knee ligaments of New Zealand White rabbits (young, age two months and adult, age thirty-six to forty months). Measurements were made from transmission electron micrographs of transverse ligament sections of approximately 50,000x magnification. Statistically significant differences in the mean fibril diameters were found between the anterior cruciate and medial collateral ligaments of the thirty-six to forty month old animals (.069 +/- .005, .092 +/- .016 mm, p < .1); however, no statistical significance was found for differences between these ligaments in two month old animals (.077 +/- .006, .082 +/- .009, p > .1). These data support the idea that known differences in fibril distributions of adult rabbit anterior cruciate and medial collateral ligaments develop with maturation, and may reflect both the cellular environment in which the fibrocytes of these ligaments are subject to, as well as the developmental genetic program of these cell populations. (+info)
The management of medial ligament tears in patients with combined anterior cruciate and medial ligament lesions.
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The management of patients with combined medial collateral (MCL) and anterior cruciate (ACL) rupture remains controversial. We studied 25 such patients who elected to have the ACL lesion treated conservatively; 14 underwent MCL repair with early mobilization and 11 were treated with immobilization for two weeks. The mean follow up was 5.9 years (2 to 11). There was no difference in the clinical assessment of ligamentous laxity, KT-1000 measurements or Tegner activity scores between the two groups but there were significantly higher Lysholm function scores in the operated group. (+info)
Low-intensity pulsed ultrasound enhances early healing of medial collateral ligament injuries in rats.
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OBJECTIVE: To investigate the effect of low-intensity pulsed ultrasound exposure on the healing of injured medial collateral ligaments. METHODS: Thirteen male Sprague Dawley rats were used in the study. After surgical transection of the bilateral medial collateral ligaments, the ligament of 1 knee received low-intensity pulsed ultrasound exposure (30 mW/cm2 for 20 minutes daily), whereas no ultrasound was applied to the contralateral knee (control side). Eight rats were killed at 12 days after surgery, and 5 rats were killed at 21 days. The bilateral knees of 5 rats were used for mechanical testing at each of the 2 periods, and 12-day specimens of the remaining 3 rats were prepared for the electron microscopic examination. The knees of 5 additional rats were used to obtain mechanical data of the normal uninjured medial collateral ligament. RESULTS: On the 12th day, the low-intensity pulsed ultrasound-treated side exhibited significantly superior mechanical properties when compared with the control side in ultimate load, stiffness, and energy absorption (P < .05). However, the treatment did not afford any mechanical advantage when tested on the 21st day. The mean diameter of the fibril was significantly larger on the treatment side than on the control side (P < .05). CONCLUSIONS: Low-intensity pulsed ultrasound exposure is effective for enhancing the early healing of medial collateral ligament injuries. (+info)
Effect of pregnancy on joint contracture in the rat knee.
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As there is evidence that ligamentous laxity is affected by the female hormones, we hypothesized that hormonal changes occurring during pregnancy could have a therapeutic role in preventing the development of a joint contracture. Knee joint contractures were created in pregnant and nonpregnant rats. After 2 wk of immobilization, the degree of contracture was measured with structural properties of the medial collateral and anterior cruciate ligaments and the pubic symphysis. Although not statistically significant, there was a general trend toward reduced contracture in pregnant compared with nonpregnant rats. Cutting the posterior capsule significantly decreased contracture for both the pregnant and nonpregnant groups, confirming the contribution of capsular structures to contracture. Ultimate loads of the medial collateral and anterior cruciate ligaments significantly decreased after immobilization compared with control, but there was no significant effect due to pregnancy. Stiffness and ultimate load of the pubic symphysis were not significantly different between pregnant and nonpregnant groups. The trend toward reduced contracture with pregnancy points toward a possible therapeutic role for female hormones in the prevention of postoperative and/or posttraumatic joint contracture. (+info)
The cellular networks of normal ovine medial collateral and anterior cruciate ligaments are not accurately recapitulated in scar tissue.
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The purpose of this study was to characterize the cellular organization of the ovine medial collateral ligament (MCL) and anterior cruciate ligament (ACL) and compare this organization with that found in ligaments undergoing healing. Indirect immunofluorescence microscopy, used in combination with antibodies to cytoskeletal proteins, was employed to visualize individual ligament cells. Normal ligaments contained fusiform cells arranged in rows, which were stacked at regular intervals across the body of the ligament forming a three-dimensional cellular lattice. Each cell exhibited prominent cytoplasmic processes that extended for long distances through the extracellular matrix to adjacent cells, and these processes contained gap junctions. Thus the cells in rows and between rows were interconnected. The cells of the MCL and ACL scars were also arranged in rows, but these rows were shorter, irregularly arranged and closely packed into bundles resulting in tissue with a higher cellular density. In addition, cells transiting the cell cycle were detected in the scar but not in normal ligament. While the rows of cells in the normal ligament extended along the long axis of the ligament, the bundles of rows of ligament scar cells had a random orientation with respect to one another and to the region outside the scar. Over time both the ACL and the MCL scars displayed discontinuities in their cellular rows. In contrast to the scars of the MCL, which contained discontinuities filled with cellular projections and gap junctions, ACL scars contained discontinuities that were devoid of cells and gap junctions. These discontinuities as well as the differences between normal and scar cytoarchitecture may represent features of an inadequate healing response and/or may provide the structural basis for the altered biomechanics of healing ligaments. (+info)
Exogenous transforming growth factor beta 1 alone does not improve early healing of medial collateral ligament in rabbits.
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OBJECTIVE: To determine whether transforming growth factor beta 1 (TGF-beta1) improves early ligament healing. DESIGN: Experimental, controlled study of medial collateral ligaments (MCLs) in rabbits' knees. SETTING: Research laboratory. SUBJECTS: Sixteen skeletally mature, New Zealand White female rabbits. INTERVENTIONS: Ten rabbits had a standardized gap injury made in the MCL of both knees. Three weeks later, a second operation was performed to inject 7 microg of TGF-beta1 in a carrier solution into the right knee MCL, while the left knee MCL was injected with carrier alone. The rabbits were killed 3 weeks after the injection of TGF-beta1 (6 weeks after the original injury). Six of the rabbits (12 knees) had no operation on the MCL and served as external normal controls. OUTCOME MEASURES: Biomechanical measures of the femur-MCL-tibia complex. Histologic evaluation of MCL cell and matrix organization. Transmission electron microscopy measures of MCL fibril diameters. RESULTS: There were no statistically significant differences in the biomechanical measures, fibril diameter distributions and histologic evaluation of the injured MCLs treated with TGF-beta1 or carrier alone. Both groups of injured MCLs were significantly different from normal MCLs. CONCLUSIONS: The results indicate that the dosage and route of delivery of TGF-beta1 did not lead to overt improvement in the healing of the injured MCL. Whether different doses or delivery methods, alone or in combination with TGF-beta1, or other growth factors would lead to improvement remains to be determined. (+info)
Mechanical effects of the intraarticular administration of high molecular weight hyaluronic acid plus phospholipid on synovial joint lubrication and prevention of articular cartilage degeneration in experimental osteoarthritis.
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OBJECTIVE: To examine in vivo the effects of a mixture of high molecular weight hyaluronic acid (HA) plus phospholipids on joint lubrication and articular cartilage degeneration. METHODS: Experimental osteoarthritis (OA) of the right knee was induced by anterior cruciate and medial collateral ligament transection in 40 rabbits. The animals were subjected to 8 consecutive weekly intraarticular administrations of high molecular weight HA (the HA200 group), conventional molecular weight HA (the HA80 group), or high molecular weight HA plus L-delta dipalmitoyl phosphatidylcholine liposomes (the PHA group) and were killed 1 week after the final injection. The remaining transected right knees (the OA group) and randomly selected nontransected contralateral left knees (the control group) were collected simultaneously. Each group (n = 10) was divided into 2 equal subgroups, one of which was evaluated histologically while the other was subjected to a lubricating ability test using a pendulum friction tester. RESULTS: The injected knees had a tendency to demonstrate less damage to the articular cartilage compared with the OA group, and the histologic findings in all groups except for the PHA group differed significantly from the control group. There was a significant difference in the mean +/- SD friction coefficient between the control group (0.0100 +/- 0.00300) and the OA (0.0206 +/- 0.00649), HA200 (0.0190 +/- 0.00427), and HA80 (0.0177 +/- 0.00712) groups (P < 0.05 for each comparison), but not between the control group and the PHA group (0.0150 +/- 0.00330) (P = 0.15). CONCLUSION: To our knowledge, this is the first in vivo study to examine whether intraarticular injections of phospholipids influence joint lubrication by acting as a boundary lubricant, thus protecting articular cartilage from degenerative changes. (+info)