Patellar component stability improves with pulsatile lavage in total knee arthroplasty.
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In a cadaver study, we prepared 37 fresh frozen human patella pairs to determine the efficacy of jet lavage in comparison to syringe lavage with respect to cement penetration and stability of the polyethylene patellar component after patellar resurfacing. For 12 patella pairs, sagittal sections were obtained at predefined levels using a diamond saw. Cement penetration was significantly greater (P<0.0001) in the jet lavage specimens compared to the syringe lavage specimens. For the remaining 25 patella pairs, pullout tests were performed on patellar components using a traction-compression device. The maximum force required to cause mechanical failure was significantly greater (P<0,0001) in jet lavage specimens compared to syringe lavage specimens. Our results support the routine use of jet lavage for cleansing the patellar bed prior to cement application in cemented patellar resurfacing. (+info)
Effect of strength training on human patella tendon mechanical properties of older individuals.
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This study investigated the effect of strength training on the mechanical properties of the human patella tendon of older individuals. Subjects were assigned to training (n = 9; age 74.3 +/- 3.5 years, body mass 69.7 +/- 14.8 kg and height 163.4 +/- 9.1 cm, mean +/- S.D.) and control (n = 9; age 67.1 +/- 2 years, body mass 73.5 +/- 14.9 kg and height 168.3 +/- 11.5 cm) groups. Strength training (two series of 10 repetitions at 80 % of five-repetition maximum) was performed three times per week for 14 weeks using leg extension and leg press exercises. Measurements of tendon elongation during a ramp isometric knee extension were performed before and after training and control periods in vivo using ultrasonography. Training caused a decreased tendon elongation and strain at all levels of force and stress (P < 0.01). Baseline tendon elongation and strain at maximal tendon load were 4.7 +/- 1.1 mm and 9.9 +/- 2.2 %, respectively (maximum force: 3346 +/- 1168 N; maximum stress: 40 +/- 11 MPa). After training, these values decreased to 2.9 +/- 1.2 mm and 5.9 +/- 2.4 % (P < 0.01), respectively (maximum force: 3555 +/- 1257 N; maximum stress: 42 +/- 11 MPa). Tendon stiffness increased by 65 % (2187 +/- 713 to 3609 +/- 1220 N mm-1; P < 0.05) and Young's modulus increased by 69 % (1.3 +/- 0.3 to 2.2 +/- 0.8 GPa; P < 0.01). As a result of these changes, the rate of torque development increased by 27 % (482.8 +/- 302.5 to 612.6 +/- 401 N m s-1; P < 0.01) following training. No significant changes occurred in any measured variables in the control group (P > 0.05). This study shows for the first time that strength training in old age increases the stiffness and Young's modulus of human tendons. This may reduce the risk of tendon injury in old age and has implications for contractile force production and the rapid execution of motor tasks. (+info)
Sex differences in knee cartilage volume in adults: role of body and bone size, age and physical activity.
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OBJECTIVE: To test the hypothesis that sex differences in knee cartilage volume may be mediated through body and bone size, age and/or physical activity. METHODS: A cross-sectional convenience sample of 372 subjects (males 43%; mean age 45 yr, range 26-61) was studied. Articular cartilage volumes and bone size were determined at the patella, medial and lateral tibia by processing images acquired in the sagittal plane using T1-weighted fat saturation magnetic resonance imaging. Height, weight, physical activity (lower limb muscle strength, endurance fitness and questionnaire items) and radiographic osteoarthritis (ROA) were measured. RESULTS: Gender explained 33-42% of the variation in knee cartilage volumes (all P < 0.001). Males had 33-42% higher cartilage volume than females at all sites. In the whole group, the magnitude of sex differences decreased to 8-18% after adjustment for body height, weight and bone size, but remained significant (all P < 0.05). Further adjustment for physical activity had no effect on the sex differences. The sex differences in cartilage volume were greater in those aged over 50 compared with those aged under 50 (P < 0.05 for age-sex interaction at all sites) and were independent of ROA. CONCLUSIONS: Men have substantially higher knee cartilage volumes than women. These sex differences appear to be mediated in part by body and bone size but a significant amount remains unexplained. Furthermore, the differences become more marked over the age of 50 yr suggesting that both cartilage development and cartilage loss in later life contribute to sex differences in cartilage volume. Further longitudinal studies in large samples will be required to confirm these findings. (+info)
Physical indicators of cartilage health: the relevance of compliance, thickness, swelling and fibrillar texture.
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This study uses a bovine patella model to compare the relative merits of on-bone compliance and thickness measurements, free-swelling behaviour, and structural imaging with differential interference contrast (DIC) light microscopy to assess the biomechanical normality of the cartilage matrix. The results demonstrate that across a spectrum of cartilage tissues from immature, mature, through to mildly degenerate, and all with intact articular surfaces, there is a consistent pattern of increased free swelling of the isolated general matrix with age and degeneration. High swelling was always associated with major structural alterations of the general matrix that were readily imaged using DIC light microscopy. Conversely, for all tissue groups, no relationship was observed between thickness vs. compliance and compliance vs. general matrix swelling. Only in the proximal aspects of the normal mature and degenerate tissues was there a correlation between thickness and general matrix swelling. Free-swelling measurements combined with fibrillar texture imaging using DIC light microscopy are therefore recommended as providing a reliable and quick method of assessing the biomechanical condition of the cartilage general matrix. (+info)
Templates of the cartilage layers of the patellofemoral joint and their use in the assessment of osteoarthritic cartilage damage.
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OBJECTIVE: To develop a methodology for generating templates that represent the normal human patellofemoral joint (PFJ) topography and cartilage thickness, based on a statistical average of healthy joints. Also, to determine the cartilage thickness in the PFJs of patients with osteoarthritis (OA) and develop a methodology for comparing an individual patient's thickness maps to the normal templates in order to identify regions that are most likely to represent loss of cartilage thickness. DESIGN: The patella and femur surfaces of 14 non-arthritic human knee joints were quantified using either stereophotogrammetry or magnetic resonance imaging. The surfaces were aligned, scaled, and averaged to create articular topography templates. Cartilage thicknesses were measured across the surfaces and averaged to create maps of normal cartilage thickness distribution. In vivo thickness maps of articular layers from 33 joints with OA were also generated, and difference maps were created depicting discrepancies between the patients' cartilage thickness maps and the normative template. RESULTS: In the normative template, the surface-wide mean+/-SD (maximum) of the cartilage thickness was 2.2+/-0.4mm (3.7mm) and 3.3+/-0.6mm (4.6mm) for the femur and patella, respectively. It was demonstrated that difference maps could be used to identify regions of thinner-than-normal cartilage in patients with OA. Patients were shown to have statistically greater regions of thin cartilage over their articular layers than the normal joints. On average, patients showed deficits in cartilage thickness in the lateral facet of the patella, in the anterior medial and lateral condyles, and in the lateral trochlea of the femur. CONCLUSIONS: This technique can be useful for in vivo clinical evaluation of cartilage thinning in the osteoarthritic patellofemoral joint. (+info)
Secondary resurfacing of the patella for persistent anterior knee pain after primary knee arthroplasty.
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Out of a total of 623 patients who, over a ten-year period, underwent primary total knee replacement (TKR) without patellar resurfacing, 20 underwent secondary resurfacing for chronic anterior knee pain. They were evaluated pre- and postoperatively using the clinical and radiological American Knee Society score. The mean follow-up was 36.1 months (12 to 104). The mean knee score improved from 46.7 to 62.2 points and the mean functional score from 44.7 to 52.2 points. Only 44.4% of the patients, however, reported some improvement; the remainder reported no change or deterioration. The radiographic alignment of the TKR did not influence the outcome of secondary resurfacing of the patella. Complications were noted in six of the 20 patients including fracture and instability of the patella and loss of movement. Anterior knee pain after TKR remains difficult to manage. Secondary resurfacing of the patella is not advocated in all patients since it may increase patient dissatisfaction and hasten revision. (+info)
Tissue-engineered cartilage and bone using stem cells from human infrapatellar fat pads.
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Multipotential processed lipoaspirate (PLA) cells extracted from five human infrapatellar fat pads and embedded into fibrin glue nodules, were induced into the chondrogenic phenotype using chondrogenic media. The remaining cells were placed in osteogenic media and were transfected with an adenovirus carrying the cDNA for bone morphogenetic protein-2 (BMP-2). We evaluated the tissue-engineered cartilage and bone using in vitro techniques and by placing cells into the hind legs of five severe combined immunodeficient mice. After six weeks, radiological and histological analysis indicated that the PLA cells induced into the chondrogenic phenotype had the histological appearance of hyaline cartilage. Cells transfected with the BMP-2 gene media produced abundant bone, which was beginning to establish a marrow cavity. Tissue-engineered cartilage and bone from infrapatellar fat pads may prove to be useful for the treatment of osteochondral defects. (+info)
The origin of cells that repopulate patellar tendons used for reconstructing anterior cruciate ligaments in man.
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Cryopreserved patellar tendon allografts are often recommended for reconstruction of anterior cruciate ligaments (ACLs) because living donor fibroblasts are thought to promote repair. Animal studies, however, indicate that ligaments regenerate from recipient rather than donor cells. If applicable to man, these observations suggest that allograft cell viability is unimportant. We therefore used short tandem repeat analysis with polymerase chain reaction (PCR) amplification to determine the source of cells in nine human ACLs reconstructed with cryopreserved patellar tendon allografts. PCR amplification of donor and recipient DNA obtained before operation and DNA from the graft obtained two to ten months after transplantation revealed the genotype of cells and showed only recipient cells in the graft area. Rather than preserve the viability of donor cells, a technique is required which will facilitate the introduction of recipient cells into patellar tendon allografts. (+info)