Experimental osteoarthritis in the rabbit knee joint

Antiresorptive therapy conserves some periarticular bone and ligament mechanical properties after anterior cruciate ligament disruption in the rabbit knee

The purpose of this study was to assess, in an osteoarthritic (OA) model, whether bisphosphonate (BP) antiresorptive therapy altered periarticular bone and bone-ligament biomechanics and OA progression. We surgically transected the anterior cruciate ligament (ACLX) in two groups of rabbits; the first group was dosed with BP (risedronate, 0.01 mg/kg s.c. daily for 6 wk), the second group remained untreated, and a third group of normal (unoperated) control rabbits was also evaluated. We measured distal femoral bone mineral density (BMD, Dual Energy X-ray Absorptiometry [DEXA]), medial collateral ligament (MCL) laxity, and bone mechanical function (bone cores mechanically tested in compression). These measures were related to cartilage/joint gross morphology, histology, and measures of vascular volume (gelatin-dye perfusion) for evidence of inflammatory angiogenesis and early OA. BMD by DEXA in 6 wk ACLX animals was 18% less than normal controls (p<0.05). In contrast, BP dosing conserved periarticular BMD; risedronate-treated rabbits had distal femoral BMD only 5% less and not significantly different than normal controls. When the same bone cores were compressed to failure, both ACLX and BP-dosed animals were significantly weaker than normal controls (p<0.05). However, the bone energy to failure and elastic modulus of BP-dosed animals was conserved and not significantly different from normal controls 6 wk after ACLX. Blocking bone resorption with BP also resulted in a significantly improved bone-ligament structural complex. MCL-complex laxity was significantly less in BP-dosed animals (1.2 times that of normal controls) compared to untreated ACLX animals (1.7 times that of normal controls; p<0.05). Blocking bone resorption with risedronate did not suppress osteophytosis and inflammatory angiogenesis, which were significantly increased in the periarticular bone of both untreated and BP treated ACLX animals. Thus, administering BP immediately after ACL loss conserved some periarticular bone and MCL-complex properties in an early OA model.

Design and validation of an unconstrained loading system to measure the envelope of motion in the rabbit knee joint

An unconstrained loading system was developed to measure the passive envelope of joint motion in an animal model commonly used to study ligament healing and joint arthritis. The design of the five-degree-of-freedom system allowed for unconstrained knee joint loading throughout flexion with repeated removal and reapplication of the device to a specimen. Seven New Zealand White rabbit knees were subjected to varus, valgus, internal and external loads, and the resulting envelopes of motion were recorded using an electromagnetic tracking device. Intra-specimen reproducibility was excellent when measured in one specimen, with maximal rotational differences of 0.6 and 0.3 deg between the fourth and fifth testing cycles for the varus (VR) and valgus (VL) envelopes, respectively. Similarly, the maximal internal (INT) and external (EXT) envelope differences were 0.5 and 0.4 deg, respectively, between the fourth and fifth cycles. Good inter-animal envelope reproducibility was also observed with consistent motion pathways for each loading condition. A maximal VR-VL laxity of 17.9 +/- 2.3 deg was recorded at 95 deg flexion for the seven knees tested. The maximal INT-EXT laxity of 75.2 +/- 4.8 deg occurred at 50 deg flexion. Studies on measurement reproducibility of re-applying individual testing components demonstrated a maximal error of 1.2 +/- 0.7 deg. Serial removal and re-application (test-retest) of the complete measuring system to one cadaveric knee demonstrated maximal envelope differences of less than 0.7 deg for VR-VL rotation and 2.1 deg for INT-EXT rotation. Our results demonstrate that the measuring system is reproducible and capable of accurate evaluation of knee joint motion. Baseline in vitro data were generated on normal joint kinematics for future in-vivo studies with this system, evaluating ligament healing and disease progression in arthritis models.

Use of microscopical techniques in the study of human chondrocytes from osteoarthritic cartilage: an overview

Several microscopical techniques, such as high resolution light microscopy, Normaski microscopy, laser confocal and transmission electron microscopy, were used in a correlative morphological study of human osteoarthritic (OA) cartilage. Emphasis was made on the characterization of chondrocytes heterogeneity observed in this tissue. Novel findings were assessed in the morphological and immunocytological study of the chondrocytes organized in aggregates or "clones" typical of this degenerative disease, consisting of the modification of certain elements of the cytoskeleton that influence changes in the cell shape. Also, the presence of cilia and centrioles found in certain cell raised the question if chondrocytes are able to move and regroup as an alternative mechanism to mitosis in the formation of cell clusters or "clones." The presence of two types of secretory chondrocytes was observed and discussed. The use of a correlative approach of several microscopical techniques in a systematic morphological and immunocytological characterization of chondrocyte population within the fibrillated and nonfibrillated human osteoarthritic cartilage gave complementary information that could be important for a better understanding of the histopathogenesis of OA.

Reconstruction of the anterior cruciate ligament

Ligaments are strong collagenous structures that act as constraints on joint motion, thus confining the articular surfaces to more or less the same paths. In so doing they prevent arbitrary apposition of these surfaces from occurring and resulting in abnormal stresses which may damage the joint surfaces. Ligaments rupture due to excessive loads, particularly those resulting from trauma occurring during sporting events or motor vehicle accidents. Knee and ankle joints have the highest frequency of ligamentous injuries. This paper is a brief review of the current approaches to the reconstruction of the knee ligaments with specific reference to the anterior cruciate ligament (ACL) being the most frequently reconstructed. This is not only because it is frequently injured but also because of the debilitating consequences of such an injury. Approaches ranging from the conservative to those that advocate the use of frank prosthetic replacement have been adopted by surgeons at both ends of the spectrum. Following a discussion of the rationale for reconstruction of the ACL, the mechanical and biological considerations of the reconstructive procedure are discussed. The different methods of ACL reconstruction are reviewed. These include: (a) primary repair, (b) reconstruction with different tissues, including autogenous allografts and xenografts, (c) reconstruction employing different synthetic devices. A brief discussion of the procedures used for reconstruction with different types of tissue and of the surviving examples of the synthetic devices will follow.

Proteoglycan alterations during developing experimental osteoarthritis in a novel hip joint model

Degenerative hip joint disease was induced in dogs by extra-articular surgery that created a condition that mimics hip dysplasia. Decreased acetabular coverage of the femoral head gave altered mechanical load, with ensuing cartilage degeneration. For comparison, degenerative knee joint disease was induced in other dogs by transection of the anterior cruciate ligament of the knee. The femoral head articular cartilage showed macroscopic signs of degeneration within a month. No macroscopical changes of synovitis were present. Chemical analysis of cartilage samples showed loss of proteoglycans. Guanidine hydrochloride extracts of the cartilage contained proteoglycan fragments that could be separated by equilibrium density gradient centrifugation in cesium chloride. The data indicate that proteoglycans are fragmented by proteolytic cleavage and lost from the cartilage. The proteoglycans remaining in the tissue are smaller and have lost the ability to aggregate with hyaluronic acid. Similarly, in experimental knee joint osteoarthritis, the proteoglycan content of the cartilage decreased. The structural changes of those proteoglycans remaining were of a different nature, with no changes in proteoglycan size or aggregation properties, possibly indicating that both degradation and repair took place in the knee articular cartilage and/or that fragments were rapidly lost from the tissue. This may follow from different surgical procedures, only the one used for the hip joint being extra-articular, or from the different anatomy and physiology of the hip joint and the knee joint.

Indomethacin influences Moloney's sarcoma and associated periosteal osteogenesis in the mouse

The effect of indomethacin on periosteal osteogenesis mediated by the Moloney sarcoma virus was studied using a mouse model. In the indomethacin-treated animals, the development of sarcoma was inhibited, as evaluated by the tumor incidence, tumor size, and maximal tumor duration. Periosteal osteogenesis mediated by this sarcoma was lower than in saline-treated control mice.

Oxygen consumption, diffusing capacity and blood flow of the synovial membrane in osteoarthritic rabbit knee joints

In osteoarthritis the changes of the synovial membrane may seriously alter the oxygen transfer characteristics from the capillaries of the membrane to the synovial fluid and hence impede or deprive the joint cartilage of its sole source of oxygen. In the present study we have estimated the blood flow (Q), diffusing capacity (DO2) and oxygen consumption (VO2) of the synovial membrane in the chronic non effusive stage of experimental osteoarthritis. In 14 osteoarthritic knee joints we found a statistically significant increase in oxygen consumption, compared to previously reported results from normal joints, whereas the diffusing capacity and the blood flow were unchanged. The implication of this is that the partial pressure difference required to overcome the increased oxygen consumption was increased with a factor 4.3 and that the oxygenation of the joint cartilage was reduced with approx. 30 Torr.

Metabolic and haemodynamic changes in the pathologic hypermobile spine

The purpose of the study was to evaluate whether pathologic hypermobility of the lumbar spine could produce haemodynamic, metabolic, and histologic changes similar to those found in osteoarthritis. Five adult goats were surgically made hypermobile in the lumbar spine by an extensive laminectomy involving exarticulation of the facet joints of the L4 and L5 levels. Seven months following the operation oxygen partial pressure (pO2), was measured in situ in the nucleus pulposus and in the adjacent lumbar body of the hypermobile segment. A segment three levels more cranially served for control. Mass spectrometry was used for continuous registration of pO2. Intraosseous pressure (IOP) was measured in the lumbar bodies of the same levels. Hypermobility averaged a 60 per cent increase at the operated segment as measured on flexion-extension radiograms preoperatively and 7 months postoperatively. The hypermobile discs had decreased in height as measured by CT scanning and this was confirmed by histologic sections. Significant hypoxia was found in the nucleus pulposus of the hypermobile segment, while increased pO2 and IOP existed in the adjacent lumbar body.

Synovitis causes hypoxia and acidity in synovial fluid and subchondral bone

The purpose of the present study was to evaluate the environmental changes in synovial fluid and subchondral bone during synovitis in rabbits in which the knee joint on one side was subjected to a procedure causing instability; a traumatic synovitis rapidly developed. Three weeks following the procedure, partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2) and hydrogen ion concentration (pH) were measured in vivo in the juxta-articular bone and in the synovial fluid of both the normal and the affected sides. Mass spectrometry was used for simultaneous registration of PO2 and PCO2, while a monocrystalline antimony pH electrode was used for simultaneous measurement of pH in vivo. Hypoxia, hypercapnia and relative acidity were found in synovial fluid and subchondral bone of knees with synovitis. The metabolic environment of synovial fluid and subchondral bone was considerably changed at the 3-week stage of experimental osteoarthritis and this was probably secondary to regional venous congestion.

Followup of the acute nonoperated isolated anterior cruciate ligament tear

This report is an attempt to analyze what happens to an isolated ACL tear that is treated nonoperatively. The results of 40 patients treated initially by nonoperative means for this injury and followed an average of 4 years are reported. A very small percentage of these patients had associated meniscal pathology. Secondary reconstructive surgery was necessary in 12 patients (30%). Primary meniscal tears were present in 4 of 25 knees (16%) and secondary meniscal tears occurred in an additional four of the patients. Giving way was a problem for 36 (86%) of the nonoperated patients, but pain and swelling were not significant problems for most. Full return to unlimited athletic activities was possible for only four (14%) of the patients. Objective signs of ACL insufficiency could be demonstrated on all patients upon clinical examination at followup. Overall grading of the knees revealed 87.5% fair or poor results.

Hemodynamics and metabolism in arthrosis. Studies in the rabbit knee

Arthrosis was induced in the rabbit knee, making it unstable by ligament resection. Acidity and hypercapnia were found in the synovial fluid of the arthrotic knees, whereas oxygen partial pressure was normal. In arthrotic subchondral bone the intraosseous pressure and oxygen partial pressure were increased; intraosseous phlebography showed venous congestion. Histologic specimens showed increased subchondral bone formation, loss of cartilage and total depletion of glycosaminoglycans. The synovial membrane was hyperplastic and fibrosis was found in the underlying tissue. We suggest that changes in environmental haemodynamics and metabolism, although secondary in nature, may play an important role in the arthrotic process.

Subchondral PO2 and PCO2 are unaffected in experimental arthrosis

We have made comparative measurements of oxygen and carbon dioxide tensions in normal and osteoarthritic subchondral bone tissue of rabbits in the 4-month stage of unilateral experimental arthrosis of the knee. The gas tensions were measured by a mass spectrometer via a special catheter inlet system. The mean values of the oxygen tensions on the normal and the osteoarthritic side were 39.8 and 46.2 mmHg, respectively. The carbon dioxide tensions were 33.3 and 34.2 mmHg. Neither difference was significant.

Hypothesis: joints can heal

Although cartilage has a limited capacity for intrinsic repair, cells extrinsic to the cartilage can provide a mechanism for repair if the proper conditions exist. The new chondroid material produced, although not histologically or biochemically identical to mature hyaline articular cartilage, can nevertheless in many circumstances permit normal joint function and prevent further joint deterioration. The evidence suggests that joint healing results from establishing a source of cells, normalizing joint pressures, and encouraging joint motion. Much of the controversy surrounding the question of whether joints can heal results from a failure to view joint function, rather than cartilage appearance, as the most important component of the healing process, and to appreciate the significant role played by mechanical factors in promoting this response.

Experimental arthrosis. Early changes in synovial morphology and lysosomal enzyme activities

The Hulth procedure was used to induce osteoarthrosis in a knee-joint in 36 rabbits, whereupon changes in chondral and synovial morphology and lysosomal enzyme activities were studied over a period of 3 months. A significant increase in enzyme activities was observed, which was more pronounced and seemed to occur earlier in the synovial membrane than in the cartilage. The synovial morphological changes were conspicuous in an early stage of the disease process and also seemed to precede the changes in chondral morphology. The results of this study suggest an important role of the synovial membrane in the pathogenesis of osteoarthrosis.

The repair of osteochondral defects in osteoarthritic rabbit knees by the use of carbon fibre

Implants of carbon fibres and carbon fibre patches were tested for their biocompatibility in osteochondral defects in rabbits with instability induced knee osteoarthrosis. The resulting repairs were compared to control holes in which no implant was inserted. There was no apparent biodegradation when fibre bundles were implanted for periods from 2 to 18 weeks, and the carbon fibre patches appeared to induce the gross appearance of a restored joint surface, mechanically strong to loading for periods from 2 to 26 weeks. Also carbon fibre in the form of a patch promoted the healing of the osteochondral defects in osteoarthritic femora with well organised fibrous tissue over repaired subchondral bone. The use of these carbon-fibre patches is suggested as an implant material for the restoration of articular surfaces in osteoarthritis.

Experimentally induced osteoarthritis in guinea pigs: metabolic responses in articular cartilage to developing pathology

Developing osteoarthritis, surgically induced in the right hind knee joint of guinea pigs by different procedures (A or B), was studied in animals maintained on either minimal or supplemented levels of dietary vitamin C. Procedure A, consisting of transecting the anterior cruciate and major portion of the medial collateral ligaments, resulted in a slower developing and less severe form of the disease than procedure B which also included a partial menisectomy. Regardless of the surgical procedure used, animals on minimal levels of ascorbate always exhibited more severe pathology than those on high levels. When compared with controls, a significant enhancement of acid phosphatase characterized arthritic cartilage in both supplemented and minimal diet groups, although the increase was 2-fold greater in the latter. In addition, a significant elevation of arylsulfatase A and B activities was observed only in the minimal diet group. Early stages of pathology in both diet groups were characterized by formation of repair cartilage which stained strongly with Safranin O on histologic sections. As the disease progressed, pitting, ulcerations, and eburnation occurred in the minimal diet group. Cartilage weight in normal joints was greater for guinea pigs kept on high levels of vitamin C. It is likely that this stimulated synthesis of cartilage in the supplemented animals protected against the erosion of the articular cartilage which characterized the more severe disease process in the guinea pigs on minimal levels of ascorbate.

The effect of ibuprofen on the thickening, stiffening and development of degenerative changes in the rabbit knee following immobilization

The right knee of adult rabbits was immobilized in extension for 5 weeks. The rabbits were then allowed to move freely for 8 weeks. Some rabbits were given 100 mg of ibuprofen (Brufen) daily per os during the immobilization and remobilization periods. The controls were not given any drug. The development of the thickness, stiffness and degenerative changes in the knees as a result of immobilization was observed. The thickening was significantly less and the radiological changes were significantly smaller in the knees of those rabbits given ibuprofen than in the controls. There were no significant differences between the groups regarding the mobility of the immobilized knees. In the study the anti-inflammatory drug ibuprofen had a prophylactic effect on some of the pathological processes in the rabbit knee (following immobilization and resulting in progressive osteoarthritis.

Osteoarthrosis following insufficiency of the cruciate ligaments in man. A clinical study

Based on a series of 48 patients with old untreated ruptures of one or both cruciate ligaments, the development of osteoarthrotic changes was demonstrated by radiography and at operation. The changes were similar to those seen in animal experiments and developed in the same sequence. Osteophytes occurred in knees with anterior cruciate insufficiency after about 2 years; significant osteoarthrotic changes occurred after longer periods, and particularly in knees with damage to both cruciate ligaments.