Experimental arthrosis by hyperpressure.

The frequent occurrence of degenerative joint disease (DJD) pathology and the high degree of functional prejudice associated with it, justify the search for experimental models with a view to a better understanding of this pathology and its treatment. The models most commonly used resort to a sudden mechanical degradation by shock (post-contusive osteoarthritis) or to a kinematic disruption of the joint through more or less extensive menisco-capsulo-ligamentary lesions or lesions induced by toxic substances. Cartilaginous lesions met with in human pathology are often secondary to a morphological anomaly at the origin of a hyperpressure. Maquet (1977) has suggested the bringing forward of the anterior tibial tubercle (ATT) in order to reduce the retro-patellar pressure. The drawing back by hollowing of this ATT appeared to us a suitable model for experimental osteoarthritis by hyperpressure MATERIAL AND METHOD Six adult male New Zealand rabbits, weighing at least 2.5 kg were operated. Anaesthesia was realised i.m. with Ketalar in conjunction with inhalation of ether. On the right side, a medial para-patellar incision, extending downwards, allowed us to obtain a cuneiform osteotomy of subtraction in the frontal plane (Fig. 1) behind the ATT while keeping it pedicled, fastened by means of an osteosynthesis screw, without opening the joint protected by the adipose infra-patellar ligament. The drawing back of the ATT corresponded to the disappearance of its physiological projection. The animals were sacrificed at four weeks, five weeks, two, four, six, and eight months after the operation. The animals were kept in cages. Radiographies were performed and specimens of the cartilaginous surfaces were dehydrated with acetone, treated five times with papain. Dialysis of the digestates (PD 10 Pharmacia) permitted dosage of hexuronic acid (HA), using Bitter and Muir’s (1962) technique, whose level in the sampled cartilage has been expressed in pg of HA per mg dry weight of cartilage. Knowing that HA reflects the level of chondroitin sulphate in the cartilage, the level of HA in the cartilage represents the cartilage proteoglycan content. The cartilage of the patella, the trochlea, the condyles, the tibial surfaces, and the menisci were all sampled separately. The left side of each animal was used as a control with an identical and isolated medial para-patellar incision without arthrotomy.