Altered mechanics of cartilage with osteoarthritis: human osteoarthritis and an experimental model of joint degeneration. (9/1002)

OBJECTIVE: Studies of cartilage mechanics seek to determine the fundamental relationships between mechanical behavior and the composition and structure of healthy cartilage and to determine mechanisms for changes associated with degeneration. METHOD: The mechanics of normal and osteoarthritic (OA) human articular cartilage are reviewed. Studies of the initiation and pathogenesis of cartilage degeneration in the anterior cruciate ligament transection (ACLT) model of joint instability are also presented. RESULTS: In human cartilage with OA, tensile, compressive and shear behaviors are dramatically altered. These changes present as decreases in the modulus or stiffness of OA cartilage in tension, compression and shear loading, and increases in the propensity to swell as compared to healthy cartilage. In the ACL transection model of OA, similar changes in the mechanics of cartilage have been observed. In addition, changes in structure, composition, and as metabolism consistent with human OA have been found. Deterioration of the collagen-proteoglycan solid network, which appears to be focused at the articular surface, has been the earliest cartilage changes in the model. It remains to be determined if the initial disruption of the cartilage surface is a direct result of mechanical forces or a product of altered chondrocyte activity. CONCLUSIONS: These data and continued research using experimental models of OA provide a basis for our understanding of the pathogenesis and the time course of events in OA and will lead to the development of better procedures for disease intervention and treatment.  (+info)

Injury and reconstruction of the anterior cruciate ligament and knee osteoarthritis. (10/1002)

OBJECTIVE: The objective of this study was to study injury and reconstruction of the anterior cruciate ligament (ACL) and their effects on knee osteoarthritis. DESIGN: This manuscript discusses the function of knee ligaments, including the basic mechanical properties, the structural properties of their respective bone-ligament-bone complexes, as well as their time- and history-dependent viscoelastic characteristics. The in-situ forces in the ACL and its replacement grafts and knee kinematics before and after ACL reconstruction are also examined. RESULTS: A robotic/universal force-moment sensor (UFS) testing system has been developed which offers a unique method in determining the multiple-degree of freedom knee kinematics and in-situ forces in human cadaveric knees. Under a 110 N anterior tibial load we found at flexion angles of 15 degrees or lower, there was a significantly larger in-situ force in the PL bundle (approximately 75 N) of the ACL as compared to the AM bundle (approximately 35 N)(P < 0.05). We also found that a quadruple semitendinosus and gracilis tendon ACL graft may be better at fully restoring in-situ forces for the whole range of knee flexion when compared to a bone-patellar tendon-bone ACL graft. CONCLUSIONS: The robotic/UFS testing system allows us to determine knee kinematics and the in-situ forces in cadaveric knees in a non-invasive, non-contact manner. Additionally, the ability to reproduce kinematics during testing allows us to evaluate ACL and ACL graft function under external and simulated muscle loading conditions. Finally, we can also examine many of the variables of ACL reconstructions that affect knee kinematics and graft forces including graft tensioning, graft type, graft placement and tibial positioning during graft fixation.  (+info)

Femoral intercondylar notch measurements in osteoarthritic knees. (11/1002)

METHODS: We measured the dimensions of the intercondylar notch of the femur in 32 patients with primary severe osteoarthrosis (OA) of the knee and 54 embalmed cadaveric knees. RESULTS: There were 56 knees with morphologically normal anterior cruciate ligament (ACL), 11 knees with lax or partially ruptured ACL and 19 knees with missing ACL. The average width of the intercondylar notch in knees with lax and missing ACL was significantly narrower than that of knees with normal ACL. In addition, knees with missing ACL had a significantly smaller notch depth than knees with normal ACL. In medial compartment OA (56 knees), the notch width and depth in knees with severe OA (37 knees) were significantly smaller than those in normal (19 knees) and mild to moderate OA groups (19 knees). CONCLUSION: Our results indicate that osteophyte growth in the femoral intercondylar notch seems to correlate with the progression of medial compartment OA of the knee.  (+info)

Detailed analysis of proprioception in normal and ACL-deficient knees. (12/1002)

We assessed proprioception using threshold levels for the perception of knee movement at slow angular velocities (0.1 degrees/s to 0.85 degrees/s) in 20 patients with unilateral tears of the anterior cruciate ligament (ACL) and 15 age-related control subjects. Failure to detect movement was also analysed. The threshold levels of detection did not differ between the damaged and undamaged knees in the patients or between the patients and the control group. Failure to appreciate movement, however, was significantly greater in knees with ACL loss compared with the undamaged knees of patients and the control group. Our findings show a proprioceptive deficit in the absence of the ACL. Measurements of threshold levels of detection of passive movement alone are not suitable for the evaluation of proprioceptive loss in ACL deficiency; assessment of failure to appreciate movement is essential.  (+info)

Arthroscopic reconstruction of the anterior cruciate ligament with patellar-tendon autograft and interference screw fixation. The results at seven years. (13/1002)

Deficiency of the anterior cruciate ligament (ACL) is a common disorder which can lead to changes in lifestyle. We followed 59 patients who had had arthroscopic reconstruction of the ACL using a central-third patellar-tendon autograft for seven years to assess the long-term effectiveness of recent advances in reconstruction of the ACL. The standard criteria for evaluation of the International Knee Documentation Committee, the Lysholm knee score and measurements using the KT 1000 arthrometer all showed satisfactory results. Deterioration in the clinical performance after seven years was associated with osteoarthritic changes and correlated with chronic ligament injuries and meniscectomy. There were three traumatic and three spontaneous ruptures. We believe that the procedure can be successful, but remain concerned about failure of the graft and osteoarthritis. The results raise questions about the best time to operate and suggest that early surgery may reduce the risk of osteoarthritis.  (+info)

The regeneration of sensory neurones in the reconstruction of the anterior cruciate ligament. (14/1002)

We examined whether somatosensory evoked potentials (SEPs) were detectable after direct electrical stimulation of injured, reconstructed and normal anterior cruciate ligaments (ACL) during arthroscopy under general anaesthesia. We investigated the position sense of the knee before and after reconstruction and the correlation between the SEP and instability. We found detectable SEPs in all ligaments which had been reconstructed with autogenous semitendinosus and gracilis tendons over the past 18 months as well as in all cases of the normal group. The SEP was detectable in only 15 out of 32 cases in the injured group, although the voltages in the injured group were significantly lower than those of the controls. This was not the case in the reconstructed group. The postoperative position sense in 17 knees improved significantly, but there was no correlation between it and the voltage. The voltage of stable knees was significantly higher than that of the unstable joints. Our findings showed that sensory reinnervation occurred in the reconstructed human ACL and was closely related to the function of the knee.  (+info)

The connective-tissue envelope in revascularisation of patellar tendon grafts. (15/1002)

Free patellar tendon grafts used for the intra-articular replacement of ruptured anterior cruciate ligaments (ACL) lack perfusion at the time of implantation. The central core of the graft undergoes a process of ischaemic necrosis which may result in failure. Early reperfusion of the graft may diminish the extent of this process. We assessed the role of peritendinous connective tissue in the revascularisation of the patellar tendon graft from the day of implantation up to 24 days in a murine model using intravital microscopy. The peritendinous connective-tissue envelope of the graft was either completely removed, partially removed or not stripped before implantation into dorsal skinfold chambers of recipient mice. Initial revascularisation of the grafts with preserved peritendinous connective tissues began after two days. The process was delayed by five to six times in completely stripped patellar tendons (p < 0.05). Only grafts with preserved connective tissues showed high viability whereas those which were completely stripped appeared to be subvital. The presence of peritendinous connective tissues accelerates the revascularisation of free patellar tendon grafts.  (+info)

Degradation of cartilage type II collagen precedes the onset of osteoarthritis following anterior cruciate ligament rupture. (16/1002)

OBJECTIVE: To determine if degradation of cartilage matrix in primary osteoarthritis (OA) or in OA secondary to rupture of the anterior cruciate ligament (ACL) is a gradual response to excessive loading or an early, initiating event in the disease process. METHODS: Biopsy samples were obtained from the low-weight-bearing articular cartilage of the intercondylar notch, in patients undergoing knee arthroscopy (ACL injury) or arthroplasty (late-stage primary OA) or in controls. In some cases, biopsy samples were also removed from the high-weight-bearing articular cartilage of the femoral condyles. Biopsy specimens were extracted and assayed for total and denatured type II collagen (CII) by inhibition enzyme-linked immunosorbent assay and for proteoglycan using a colorimetric method. All patients were assessed radiographically for cartilage erosion. In addition, the cartilage of patients with ACL injury was assessed at arthroscopy, and the knee function of patients with primary OA was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). RESULTS: Increased CII degradation was detected in the low- as well as the high-weight-bearing cartilage of patients with late-stage OA, and there was a positive correlation between the percentage denatured collagen and the WOMAC score. Most of the patients with ACL injury had no clinical signs of OA or macroscopic cartilage erosion. However, the low-weight-bearing articular cartilage from these patients showed a significant increase in CII degradation, similar to that observed in late-stage OA. The proteoglycan content of articular cartilage did not change significantly in patients with OA or ACL injury compared with controls. CONCLUSION: CII degradation is an early event following ACL injury and is unlikely to be a direct result of mechanical loading, since it was observed in cartilage obtained from a low-weight-bearing site.  (+info)