Heterogeneity in patellofemoral cartilage adaptation to anterior cruciate ligament transection; chondrocyte shape and deformation with compression.
ABSTRACT The purpose of this study was to determine if the opposing cartilages of the feline patellofemoral joint adapted differently to short-term anterior cruciate ligament transection (ACL-T) and if the magnitude of chondrocyte deformation upon tissue loading was altered under ACL-T conditions compared to contralateral controls. In situ static compression of physiological magnitude was applied to the feline patellofemoral cartilage 16 weeks post-ACL-T and cartilage and chondrocyte deformation were evaluated by histomorphometry.
Six adult cats were euthanized 16 weeks after unilateral ACL-T. A peak surface pressure of 9 MPa was applied to the fully intact patella and femoral groove cartilages. After in situ fixation under compression, sections from the centre of the indent and from an adjacent unloaded area of the cartilages were analysed. Chondrocyte shape, size, clustering and volumetric fraction were quantified.
Experimental patellar articular cartilage was thicker, contained larger chondrocytes that were more frequently arranged in clusters and had, on average, a larger chondrocyte volumetric fraction compared to contralateral controls. In contrast, the experimental femoral groove cartilage demonstrated little adaptation to ACL-T.
The patellar articular cartilage adapts to short-term ACL-T to a greater extent than femoral groove cartilage. We speculate that differences in the histological parameters of control tissues, such as cartilage thickness and the magnitude and depth distribution of chondrocyte shape, size and volumetric fraction may contribute to predisposing patellar cartilage, and not femoral groove cartilage, to adaptation after ACL-T.
- SourceAvailable from: Patrick Y Wuethrich[show abstract] [hide abstract]
ABSTRACT: In this study, we investigated the depth-dependent metabolic and structural responses of adult articular cartilage to large-strain, static, unconfined compression. Changes in cell biosynthetic activity and several morphometry-based structural parameters (cell density, cell volume fraction, cell surface-area density, mean cell surface area, and mean cell volume) were measured at eight sites representing different depth-zones between the articular surface and the cartilage/bone border. In addition, local axial strain in the superficial, transitional, upper radial, and lower radial zones was estimated on the basis of the change in cell density values. Static compression of articular cartilage revealed a highly heterogeneous deformation profile through the depth of the sample as well as zone-specific changes in biosynthetic activity, as reflected by incorporation of [3H]proline. The axial strains in the top layers were greater than the applied surface-to-surface strain, whereas axial strains adjacent to the cartilage/bone border were significantly less than the applied strain. Zonal changes in cell density and axial strain that occurred during static compression correlated well with alterations in metabolic activity. These coordinated changes between cell biosynthesis and cartilage structure suggest that zone-specific variations in mechanical stimuli could be responsible for spatially varied patterns of cartilage metabolic activity under load.Journal of Orthopaedic Research 04/1997; 15(2):189-96. · 2.88 Impact Factor
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ABSTRACT: Focal chondral or osteochondral defects can be painful and disabling, have a poor capacity for repair, and may predispose patients for osteoarthritis. New surgical procedures that aim to reestablish hyaline cartilage have been introduced and the results seem promising. The purpose of this study is to provide reliable data on chondral and osteochondral defects in patients with symptomatic knees requiring arthroscopy and to calculate the prevalence of patients who might benefit from cartilage repair surgery. Prospective study. One thousand consecutive knee arthroscopies were included in this study. Immediately after each arthroscopy, the surgeon completed a questionnaire providing detailed information about the findings. Chondral and osteochondral lesions were classified in accordance with the system recommended by the International Cartilage Repair Society (ICRS). Chondral or osteochondral lesions (of any type) were found in 61% of the patients. Focal chondral or osteochondral defects were found in 19% of the patients. In these patients, 61% related their current knee problem to a previous trauma, and a concomitant meniscal or anterior cruciate ligament injury was found in 42% (n = 81) and 26% (n = 50), respectively. The mean chondral or osteochondral total defect area was 2.1 cm(2) (range, 0.5 to 12; standard deviation [SD], 1.5). The main focal chondral or osteochondral defect was found on the medial femoral condyle in 58%, patella in 11%, lateral tibia in 11%, lateral femoral condyle in 9%, trochlea in 6%, and medial tibia in 5%. It has been suggested that cartilage repair surgery may be most suitable in patients younger than 40 to 50 years old. A single, well-defined ICRS grade III or IV defect with an area of at least 1 cm(2) in a patient younger than 40, 45, or 50 years accounted for 5.3%, 6.1%, and 7.1% of all arthroscopies, respectively. Our study supports the contention that articular cartilage defects are common. It has the advantages of a prospective design and use of a new classification system recommended by the ICRS. This modern system focuses on objectively measurable parameters of the lesion's extent and not its surface appearance.Arthroscopy The Journal of Arthroscopic and Related Surgery 10/2002; 18(7):730-4. · 3.10 Impact Factor
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ABSTRACT: Long-term changes in the three-dimensional external loading, hind limb kinematics and knee stability were assessed in an anterior cruciate ligament (ACL)-transected cat model of osteoarthritis (OA). Seven skeletally mature cats (mean mass 4.6+/-1.4 kg) were studied before ACL transection (ACLT) and at 1 and 3 weeks, and at 3, 6, 9 and 12 months following ACLT. One week following ACLT, significant changes from the normal locomotion pattern were observed: peak vertical and anterior posterior ground reaction forces were decreased, particularly the peak posterior forces in the early phase of stance. Furthermore, knee angles were reduced by about 15 degrees throughout the whole gait cycle, while ankle and hip angles were reduced at paw off in the experimental compared to the contralateral hind limbs. Ground reaction forces and hind limb kinematics recovered to near pre-surgical patterns over the one year period assessed. ACLT was also associated with an increased knee instability which improved over time. X-rays suggested that there was a continued degeneration in the experimental knee over the one year period; there was osteophyte formation at the joint margins and an increase in cartilage thickness throughout the joint. It was speculated that the more flexed knee angles and the reduced anterior-posterior ground reaction forces in the ACL-transected compared to the intact hind limb represent an adaptive strategy aimed at avoiding excessive anterior displacement of the tibia in the early phase of stance. The recovery of the locomotion pattern with time might be related to the corresponding improvement of knee stability.Journal of Biomechanics 07/1998; 31(6):511-7. · 2.72 Impact Factor