Jarl-Erik Michelsson

Operative versus closed treatment of primary dislocation of the patella Similar 2-year results in 125 randomized patients

To assess whether initial surgery is beneficial for patients with primary dislocation of the patella, we carried out a prospective randomized study. Knee stability was examined under anesthesia, and associated injuries were excluded by diagnostic arthroscopy. 55 patients then had closed treatment and 70 patients were operated on with individually adjusted proximal realignment procedures. Surgery gave no benefit based on 2 years of follow-up. The subjective result was better in the non-operative group in respect of mean Houghston VAS knee score (closed 90, operative 87), but similar in terms of the patients own overall opinion and mean Lysholm II knee score. Recurrent instability episodes (redislocation or recurrent subluxation) occurred in 20 nonoperated and in 18 operated patients. Of these, 15 and 12, respectively, then suffered redislocations. Function was better after closed treatment. Serious complications occurred after surgery in 4 patients. In conclusion, the recurrence of patellar dislocation may be more frequent than reported, whatever the form of treatment. Routine operative management cannot be recommended for primary dislocation of the patella.

OSTEOARTHRITIS OF THE KNEE IN THE RABBIT PRODUCED BY IMMOBILIZATION Attempts to Achieve a Reproducible Model for Studies on Pathogenesis and Therapy

In order to obtain a reproducible experimental model of osteoarthritis a method of immobilizing the rabbits knee in extension by means of plastic splint was developed. The right knees of the rabbits were immobilized for periods varying from 4 days to 24 weeks. With the left knees as controls the knees were studied in a variety of ways among these being radiography (126 rabbits), histological sections stained with Alcian Blue (88 rabbits), analysis of 35S-sulphate uptake (22 rabbits) and 35S-autoradiography (6 rabbits). In 27 rabbits the regaining of mobility after immobilization was studied. After 5-6 weeks of immobilization most of the knees showed moderate or severe changes including loss of articular cartlilage and osteophyte formation. Immobilization of the rabbits knee by this method provokes a fairly easily reproducible type of degenerative joint disease showing similarities to advanced osteoarthritis as seen in humans.

Abnormal mitochondria and sarcoplasmic changes in rabbit skeletal muscle induced by immobilization

Immobilization of the rabbit knee in extended position results in damage to the vastus intermedius profundus (VIP) muscle. To examine the mechanisms involved in initiation of the injury, we studied the light and electron microscopic morphology of the VIP muscle, as well as the activity and distribution of NADH tetrazolium reductase (NADH‐TR) in the affected muscle, and determined serum total creatine kinase (CK) activity in immobilized rabbits. The VIP muscle of the immobilized right hindlimb was removed at various time points (10 h, 24 h, 36 h and 48–72 h, n=5 for each time point). The nonimmobilized left hindlimb and five nonimmobilized animals served as controls. No morphological changes were observed by light microscopy within 48–72 h in routine stainings. Transient ultrastructural abnormalities, including abnormal cristae, matrix lucencies and mild swelling of mitochondria, were observed between 10 h and 36 h of immobilization, subsiding by 48–72 h. On the other hand, progressive disorganization of myofibrils with breaking‐up of Z‐bands and an increase in the number and size of sarcoplasmic lipid vacuoles was seen with increasing duration of immobilization. NADH‐TR activity at subsarcolemmal locations had decreased by 10 h and disappeared by 24 h of immobilization, while the intermyofibrillar mitochondria remained unaltered. Serum total CK activity began to increase by 2 h of immobilization and reached a peak by 24 h. The results indicate that already a few hours of immobilization of the rabbit knee in extension leads to signs of metabolic disturbance of the VIP muscle and sarcolemmal leakage. The simultaneous occurrence of transient mitochondrial abnormalities, transient CK efflux and progressive myofibrillar damage suggests the operation of multiple adverse mechanisms already at the onset of disuse muscle atrophy.

Treatment of para-articular ossification after total hip replacement by excision and use of free fat transplants.

Six patients with para-articular ossification after total hip replacement were treated by excision and free fat tissue transplantation. The results of treatment were good and at the follow-up examinations, 2 to 8 years after the operation, a good range of movement of the hip joint was noted in all cases. It was apparent that the free fat transplant had prevented the recurrence of the para-articular ossification.

Bone formation in experimental myositis ossificans

The development of ectopic ossification in experimental myositis ossificans of the rabbit thigh was studied. The right hind limb of 25 rabbits was immobilized with the knee in extension. Once a day the limb was passively mobilized for 2–3 minutes. The animals were killed 3,5,7,14,21,28 and 35 days after the beginning of the experiment. Specimens for light and electron microscopy were obtained from both hind limbs. Extensive necrosis and fibrosis were observed in the right vastus intermedius muscle during the first week. Proliferation of chondrocytes and osteoblasts with newly formed woven bone and cartilage formation were found in the periosteum within 7 and 14 days after the beginning of the experiment. Intensive enchondral ossification and hard calcified tissue were observed later. It was evident that bone formation in this experimental model started in the periosteum after necrosis of the adjacent skeletal muscle. Therefore the temporal and spatial relationship of traumatic changes in the periosteum and muscle seems important for the development of myositis ossificans.

Severe degeneration of rabbit vastus intermedius muscle immobilized in shortened position.

The authors have previously shown that passive daily mobilization of the rabbit hind limb immobilized with the knee in extension leads to necrosis of the deep thigh muscles and myositis ossificans‐like periosteal bone formation. In this study the effect of immobilization alone on the rabbit hind limb muscles was examined similarly to that of immobilized limbs. Serum creatine kinase activities increased significantly and intravenously administered Evans blue albumin showed increased vascular permeability in the deep vastus intermedius muscle even on day 1. Necrotic fibers were clearly present in the deep part of the vastus intermedius muscle on day 5 in light and electron microscopy and in enzyme histochemistry. Fibrosis and atrophy were found later. The superficial portion of the vastus intermedius and the deep contralateral nonimmobilized vastus intermedius showed degenerative changes. Bone formation was not noted. The conclusion was that the deep vastus intermedius muscle composed almost exclusively of type I fibers is exceptionally prone to damage when immobilized in a shortened position. Contact of the necrotic muscle with the underlying periosteum is not alone sufficient to induce heterotopic ossification. The additional trauma caused by daily mobilization is needed for the myositis ossificans‐like bone formation.

Changes in Bone Formation During Immobilization and Development of Experimental Osteoarthritis: A Study using Oxytetracycline in Rabbits

The effect of immobilization on bone formation in the knee and hip was studied by means of oxytetracycline. One leg of 11 growing and 13 adult rabbits was immobilized so that the knee was held in extension but the hip was free. In the knee, degenerative changes developed consistently with a severity proportional to the length of the immobilization time. In most of the rabbits given oxytetracycline 1-13 days before they were killed considerably more oxytetracycline was incorporated in the bone in the immobilized knee region and slightly more in the hip region of the same leg than in the corresponding areas of the other leg. This indicates an increased turnover of bone tissue in the immobilized leg compared with the non-immobilized leg.

Early muscle changes after immobilization. An experimental study on muscle damage.

Immobilization of the rabbit knee in extension has previously been shown to damage the vastus intermedius profundus (VIP) muscle. To examine the mechanism of the early stages of the muscle damage, the authors studied creatine kinase activity in serum, and both light and electron microscopic changes in the affected muscle. The right knee was immobilized in an extended position using a splint, and thigh muscles were removed at various intervals, up to 48 hours after immobilization. The left hindlimb served as a control. Creatine kinase levels in serum rose ten hours after the onset of the immobilization. The enzyme levels reached a substantial peak by 24 hours, and plateaued thereafter. Light microscopic changes were not observed within 48 hours, but in electron microscopy distinct mitochondrial swelling and crystal abnormalities were seen as early as ten hours. The ultrastructural changes of mitochondria remained constant for up to 36 hours and decreased thereafter. At 48 hours of immobilization, also myofibrillar disorganization was seen. It appears that immobilization of the rabbit knee in extension rapidly leads to signs of remarkable damage to the VIP muscle. These suggest leakage of the cell membrane and metabolic disturbances. The ultrastructural changes observed share common features with muscle damage caused by ischemia, uncoupling agents, and inherited mitochondrial myopathies.

Resection of the Ackomion in the Treatment of Persistent Rotator Cuff Syndrome of the shoulder

Partial or complete excision of the acromion was performed in 25 patients (29 shoulders) with long-standing pain in the shoulder typical of rotator cuff syndrome. There was no verified history of trauma in nine cases (13 shoulders), while injury was the cause of pain in 16 patients (16 shoulders). In nine shoulders there was a small and in two a large rupture of the rotator cuff. Twelve of the 13 non-traumatic shoulders became painless postoperatively and the pain was relieved in one. In the 16 traumatic shoulders the relief of pain was complete in six, partial in nine, and one remained unchanged. The condition was not aggravated in any of the cases. Mobility increased postoperatively in four cases and was in no case decreased by the operation. In this series the results were as favourable after partial as after complete excision of the acromion alone or excision in combination with other procedures appears to be a promising method of treatment of patients with long-standing rotator cuff syndrome.

Isolation of bone from muscles prevents the development of experimental callus-like heterotopic bone. A study of the interaction of bone and muscle in new bone formation.

Heterotopic bone (HB) has previously been provoked in the compartment of the profundus part of the vastus intermedius muscle (VIP) by manipulation of the rabbit knee immobilized in extension. The authors isolated the femoral bone of adult rabbits with a permeable or an impermeable polymer membrane to investigate the interactions of bone, periosteum, and muscle in callus-like HB formation, using the HB model. Heterotopic bone developed beside but not over the membrane if isolation was carried out before the immobilization-manipulation period, regardless of the type of membrane used. In cases where the femoral bone was isolated from the muscle by insertion of the tubular membrane one to two weeks after the immobilization-manipulation had begun, there was HB formation over and beside the membrane. No HB developed under the membrane in any of the cases of femoral bone isolation. Thus direct and extensive contact between bone and muscle appears to be essential at the onset of formation of experimental HB. An intertissue exchange of soluble substances derived from bone or muscle, however, does not seem to play an essential role here. After the onset of HB formation, its further development will not be prevented by subsequent isolation of muscle and bone. The study elucidates the interaction between bone and adjacent muscles and the results may be valuable in further investigations on HB and fracture healing.