Robert B. Salter

Division of Orthopaedic Surgery, Hospital for Sick Children, Toronto, Ontario, Canada Division of Orthopaedic Surgery, Toronto General Hospital, Toronto, Ontario, Canada

A new concept, continuous passive motion of a synovial joint in vivo, was investigated to determine its biological effect on the healing of full-thickness articular cartilage defects that penetrate the subchondral bone of knee joints of adolescent and adult rabbits. The effect of continuous passive motion was compared with the effects of immobilization and of intermittent active motion. This investigation included assessment of 480 defects in the knees of 120 adolescent rabbits and assessment of 108 defects in the knees of twenty-seven adult rabbits. The continuous passive motion was well tolerated by these animals, whose general well-being was undisturbed. The healing of the defects at weekly intervals up to four weeks was assessed by gross examination and by an analysis of two indices of healing determined by light microscopy: (1) the nature of the reparative tissue, and (2) the degree of metachromasia of the matrix as demonstrated by toluidine-blue staining. At three weeks this assessment revealed that in the adolescent rabbits, healing of the defects by hyaline articular cartilage was present in 8 per cent of forty defects in ten animals whose knees were immobilized, in 9 per cent of forty defects in ten animals whose knees were permitted intermittent active motion, and in 52 per cent of forty defects in ten animals whose knees were managed immediately after operation by continuous passive motion. At three weeks, in the adult animals, healing of the defects by hyaline articular cartilage was present in 3 per cent of thirty-six defects in nine animals whose knees were immobilized, in 5 per cent of thirty-six defects in nine animals whose knees were permitted intermittent active motion, and in 44 per cent of thirty-six defects in nine animals whose knees were managed immediately after operation by continuous passive motion. Thus, the metaplasia of the healing tissue within the defects from undifferentiated mesenchymal tissue to hyaline articular cartilage was not only much more rapid but also much more complete with continuous passive motion than with either immobilization or intermittent active motion.

1. The problem of instability of reduction in congenital dislocation and congenital subluxation of the hip has been studied and it has been concluded that the basic cause of this instability is the abnormal direction in which the entire acetabulum faces. 2. An operation, innominate osteotomy, has been designed to correct the abnormal direction of the entire acetabulum in children over the age of eighteen months. The principle of innominate osteotomy is redirection of the acetabulum so that the reduced dislocation or subluxation, which previously was stable only in a position of abduction and flexion, is rendered stable in the functional position of weight bearing. 3. The operative technique, and the pre-operative and post-operative management are described. 4. The indications for innominate osteotomy are outlined and the advantages of the operation are enumerated. 5. The early results of innominate osteotomy are very encouraging.

An autogenous graft of tibial periosteum was sutured (with its cambium layer facing into the joint) to the base of a five by ten-millimeter full-thickness defect in the patellar groove of each of forty-five adolescent rabbits. The rabbits were randomly treated postoperatively by either four weeks of immobilization in a cast, intermittent active motion in a cage, or two weeks of continuous passive motion. One year postoperatively, the regenerated tissue from each rabbit was analyzed macroscopically, histologically, histochemically, and biochemically. Gross degenerative changes were seen in 57 per cent of the rabbits that had been immobilized in a cast, in 73 per cent of the rabbits that had been allowed intermittent active motion, and in 22 per cent of the rabbits that had been subjected to continuous passive motion (p less than 0.05). Out of a possible score of 7.0 points for the nature of the regenerated tissue, the scores for the three groups were: immobilization in a cast, 4.1 points; intermittent active motion, 4.0 points; and continuous passive motion, 5.9 points (p greater than 0.05). Out of a possible perfect combined score of 10.0 points for the structural characteristics of the regenerated tissue, the cast-immobilization group scored 3.8 points; the intermittent active-motion group, 2.5 points; and the continuous passive-motion group, 6.4 points (p less than 0.001). The total scores for freedom from cellular changes of degeneration, a perfect score being 5.0 points, were: immobilization in a cast, 2.4 points; intermittent active motion, 2.3 points; and continuous passive motion, 3.9 points (p less than 0.01). Degenerative changes in the adjacent cartilage, which were noted in 42 and 46 per cent of the knees in the immobilization and intermittent active-motion groups, respectively, were not found in the knees that had been subjected to continuous passive motion (p less than 0.05). The total indices, which were derived by combining the scores for all categories (maximum, 24.0 points), revealed that the index for the continuous passive-motion group was significantly better than the index for either of the other two groups: immobilization in a cast, 12.9 points; intermittent active motion, 11.2 points; and continuous passive motion, 19.2 points (p less than 0.0005).(ABSTRACT TRUNCATED AT 400 WORDS)

A rectangular graft of autogenous tibial periosteum was sutured (with its cambium layer facing into the joint) onto the base of a five by ten-millimeter full-thickness defect in the patellar groove of each of 143 adolescent and adult rabbits. The rabbits were managed postoperatively by either immobilization, intermittent active motion, continuous passive motion for two weeks, or continuous passive motion for four weeks. When the animals were killed four weeks postoperatively, the contour of the patellar groove had been restored in all of the rabbits in the group that had had four weeks of continuous passive motion, and the newly formed tissue in all of the defects in this group had the gross, histological, and histochemical appearance of smooth, intact hyaline articular cartilage. Histologically, the nature of the tissue that had formed, as well as its surface regularity, structural integrity, and bonding to the adjacent cartilage, were significantly better in the group that had had four weeks of continuous passive motion than in any of the other groups. The results were significantly worse when the orientation of the periosteal graft was reversed (that is, when it had been sutured into the defect with the cambium layer of the graft facing the subchondral bone rather than into the joint) or when no periosteal graft was used. Biochemical analyses revealed that, in the group that had had four weeks of continuous passive motion, the total hexosamine content, the levels of chondroitin sulphate and keratan sulphate, and the ratio of galactosamine to glucosamine were all comparable with the values for normal articular cartilage. In contrast, in the groups that were treated by immobilization, intermittent active motion, or two weeks of continuous passive motion, as well as in the adult rabbits, the content of the first three of these substances was significantly less than normal. In the groups that were treated by immobilization, intermittent active motion, or two weeks of continuous passive motion, 32 to 47 per cent of the total collagen was type II, while in the group that had had four weeks of continuous passive motion, 93 per cent of the total collagen was type II. These results demonstrate that, under the influence of continuous passive motion, free autogenous periosteal grafts can repair a large full-thickness defect in a joint surface by producing tissue that resembles articular cartilage grossly, histologically, and biochemically, and that contains predominantly type-II collagen.