Doron Norman

The effects of enoxaparin on the reparative processes in experimental osteonecrosis of the femoral head of the rat

The blood supply of one femoral head of 6‐month‐old rats was severed by incising the periosteum of the neck and cutting the ligamentum teres. The rats were killed on the 30th postoperative day and the femoral bones were obtained for semiquantification of the reparative processes in the necrotic heads. Fourteen rats were treated with enoxaparin and 14 untreated animals served as controls. Statistically, the amounts of necrotic bone in the epiphysis were less, the extent of remodeling of the femoral heads was milder, and the articular cartilage degeneration was slighter in the enoxaparin‐treated than untreated rats. There was no significant difference in the quantities of newly formed bone in femoral heads of treated and untreated rats. These findings are in agreement with the known effects of unfractionated and low‐molecular‐weight heparins which enhance osteoclastic bone resorption and angiogenesis and decrease osteoblastic bone formation. The former activities, operative in minimizing the structural distortion of the femoral head, oppose the crucial event in the pathogenesis of post‐osteonecrotic osteoarthritis.

Treatment of Graf’s Ultrasound Class III and IV Hips Using Pavlik’s Method

AbstractWhen Pavlik introduced his method of treating congenital dislocation of the hip, he emphasized reducing the rate of osteonecrosis. Graf’s method of sonographic evaluation afforded earlier accurate diagnosis and subsequent treatment of developmental dysplasia of the hip. To ascertain whether treatment duration, gender, age at diagnosis, clinical stability, and/or treatment onset correlate with the risk of osteonecrosis in Graf Type III or IV hips, we clinically and sonographically screened 18,067 neonates (36,134 hips) for developmental dysplasia of the hip over a 4-year period; 151 had Graf Type III or IV hips, and 78 of these were treated by us and had known outcomes. Of these 78 hips, 65 (0.18%) had Graf Type III and 13 (0.036%) had Graf Type IV hips. Sixteen of the 65 Type III hips (25%) reduced spontaneously. Using Pavlik’s method, reduction was achieved in 46 of 65 (88.5%) Type III hips and eight of 13 Type IV hips. None of the hips treated exclusively by Pavlik’s method developed osteonecrosis. Thus, the method achieves one of Pavlik’s original goals of decreasing osteonecrosis incidence to close to zero. Level of Evidence: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Osteoarthritis-like disorder in rats with vascular deprivation-induced necrosis of the femoral head.

The reparative processes following vascular deprivation-induced necrosis of the femoral head were studied histologically in rats sacrificed 2, 7, 14, 21, 42 and 92 days postoperatively. The blood supply was severed by incision of the periosteum at the neck of the femoral head and transection of the ligamentum teres. Granulation tissue and a well-vascularized fibrous tissue originating from the joint capsule invaded the necrotic marrow spaces. With progressive resorption of the necrotic tissues and osteoneogenesis, both appositional and intramembranous, within the fibrotic intertrabecular spaces, the remodeling process led to a shift of the normal spongy architecture of the femoral head to a compacta-like one. In a few cases, osseous bridges bisected a necrotic physeal cartilage at the latest time intervals. The remodeling was associated with flattening of the femoral heads as well as with degenerative, regenerative and reparative alterations of the articular cartilage. In one of the two femoral heads obtained three months postoperatively, cystic spaces developed in the fibrous subchondral zone. Our findings are consistent with the view that ineffective attempts at restoring the prenecrotic state of the femoral head by replacing the necrotic with viable tissue triggers the collapse of the femoral head. Thickening and condensation of the subchondral bone, leading to increased stiffness of the subchondral zone, result in the osteoarthritis-like disorder. Mimicking the well-known phases of human osteonecrosis, the model readily allows for preclinical studies of therapeutic regimens.

Cerebral microemboli during hip fracture fixation: a prospective study.

BACKGROUND: Recent studies have shown that cerebral fat microembolism takes place during surgery for hip or knee replacement. In this study, we examined the occurrence of cerebral microembolism, solid or gas, during a standard procedure of hip fracture fixation. METHODS: This was a prospective study of patients who underwent urgent surgery with a dynamic hip screw for hip fracture fixation. During surgery, patients were monitored with transcranial Doppler for detection of microemboli from right and left middle cerebral arteries. RESULTS: Twenty-two patients were included in the study; their median age was 82 yr (range, 51–97 yr). In nine (41%) patients, high intensity transient signals were recorded, indicating microemboli passage in the middle cerebral arteries. All nine patients had signals of both solid and gas emboli. One of these nine patients had a postoperative cerebrovascular accident. CONCLUSIONS: The incidence of cerebral microemboli during urgent surgery for hip fracture fixation is considerable. This phenomenon is not confined to hip or knee replacement surgery. The clinical implications of this finding require further investigation.

Use of a new exsanguination tourniquet in internal fixation of distal radius fractures.

We describe our experience using a new device that results in a bloodless field in open repair of distal radius fractures. The device, an exsanguinating tourniquet (HemaClear model/40, OHK Medical Devices, Haifa, Israel), replaces the traditional methods of limb elevation, Esmarch bandaging, pneumatic tourniquet pressurizing and the associated components. HemaClear/40 is an elastic silicon ring with a tubular elastic sleeve rolled onto it. The device has attached straps that, when pulled, unroll the sleeve, rolling the ring mesially on the limb. The pressure exerted by rolling HemaClear/40 is supra-systolic thereby exsanguinating the limb and occluding the arterial inflow. Our experience in 49 patients demonstrated quick application, superior exsanguination and that the device could be placed on the forearm instead of the upper arm. No side effects or complications were noted. In our opinion, the fact that HemaClear/40 is a sterile, single-patient device makes it superior over the traditional technology.

Intraosseous conduit-induced enhancement of ingrowth of blood vessels into the necrotic femoral head of rats

Following severance of the blood supply to the left femoral head of 6-month-old rats by incising the periosteum of the neck and cutting the ligamentum teres, a 21-gauge needle, inserted into the foveola, was pushed forward in the direction of the neck up to the opposite cortical bone. Femora were obtained for histological examination on postoperative days 32 and 42, from 22 and 12 rats, respectively. The right femoral heads were normal. In addition to the usual reparative and regressive changes characteristic of the second month after induction of osteonecrosis, the left femoral heads showed, compared to the femoral heads of otherwise untreated rats, lavish ingrowth of blood vessels and proliferation of mesenchymal cells. Moreover, 16 of the 34 femoral heads disclosed additional distinctive lesions, namely, partial fibrous replacement, surface depression, intraosseous tunneling, and subtotal destruction of the epiphysis. The results of this experiment, an attempt at modeling core decompresssion in man, parallel the frequently reported unsatisfactory outcome of the procedure in patients with osteonecrosis of the femoral head. They as well indicate that any therapeutic effects of producing an epiphyseal-metaphyseal conduit for the ingrowth of vessels and cells may only be achieved at the cost of a reduction in the mechanical load-bearing capacity of the femoral head.

Correction of distal femoral valgus deformities in adolescents and young adults using minimally invasive fixator-assisted locking plating (FALP).

The treatment of distal femoral valgus deformities in skeletally mature patients might be a challenging surgical problem with significant morbidity. Treatment options are various and include osteotomy and external fixation, intramedullary nailing, and plating using standard and locking plates. We describe technical notes of minimally invasive technique of fixator-assisted plating using a supracondylar locking plate. During a period of 3 years, we operated on six patients (seven femurs) with distal femoral valgus deformities of different etiologies. All patients achieved correction of the deformities and started full weight bearing with radiographic evidence of union 6 weeks after correction. We believe that fixator-assisted locking plating has advantages over correction using external fixation and intramedullary nailing. This method of correction can be performed by a minimally invasive technique, precisely, and with minimal morbidity.

Postosteonecrotic osteoarthritis-like disorder of the femoral head of rats.

The femoral heads of 15 rats were studied histologically 3 months after the induction of ischaemic necrosis by incising the cervical periosteum and cutting the ligamentum teres. The epiphyses consisted of immature disorganized subchondral and trabecular bone. The inter-trabecular spaces contained fibrous or haematopoietic tissue. Residual necrotic bone was rare. There was marked osteoblastic and osteoclastic activity. The articular aspect of the heads showed a spectrum of changes, ranging from cartilaginous degeneration with fibrillation and loss of glycosaminoglycans to an eburnated and polished bony surface. In seven rats, transphyseal bridges connected the epiphyseal and metaphyseal bony trabeculae to each other. It is suggested that the postnecrotic reparative processes, including the resorption of the necrotic debris and its replacement by newly formed, weak bone, led to an osteoarthritis-like disorder. This healing pattern of the necrotic femoral head was reminiscent of the progressive remodelling that occurs in rings in femoral capital osteonecrosis of adult human patients and in Perthess disease of children.

Core decompression and alendronate treatment of the osteonecrotic rat femoral head: computer-assisted analysis

Femoral head avascular necrosis is a process leading to femoral head deformity and osteoarthritic changes in the hip joint. Alendronate slows down bone resorption and remodelling in rats, while core decompression hastens the healing processes. We evaluated the influence of daily alendronate treatment on the rat femoral head shape after surgical osteonecrosis with core decompression, compared with controls. No differences were found in shape factor and femoral head height/length ratios. It was concluded that alendronate treatment slows down the process of replacing osteonecrotic bone by new bone and prevents early immature new bone collapse resulting from early revascularization because of core decompression.

Giant-cell reparative granuloma-like lesion in the femoral heads of rats during the early repair phase of osteonecrosis

We describe the unusual occurrence of giant-cell reparative granulomas in the rat. Cutting the ligamentum teres and incising the periosteum around the base of the femoral neck induced femoral capital necrosis. Giant-cell reparative granuloma-like lesions developed in ~0.8% of 366 rats during the early reparative stages of osteonecrosis. Resorption of the necrotic bone, hematopoietic tissue, and adipocytes was exceptionally widespread in these three rats. Overexpression of macrophage-fusing cytokines may account for the increased number of multinucleated giant cells, which on a plump stromal cell background imitate a giant-cell reparative granuloma of the bone.RésuméDescription d’un développement inhabituel de granulome de réparation à cellules géantes chez le rat. La section du ligament rond et l’incision du périoste à la base du col fémoral induit le développement d’une nécrose de la tête fémorale. Un granulome de réparation à cellules géantes se développe chez 0,8% de 366 rats durant la phase précoce de réparation de l’ostéonécrose. Une résorption de l’os nécrosé, du tissu hématopoéïtique et des adipocytes étaient largement présent et à titre exceptionnel chez ces 3 rats. Une sur-expression de cytokines créatrices de macrophages doit compter pour expliquer le grand nombre de cellules géantes, qui dans un environnement de stroma graisseux imitent un granulome à cellules géantes de réparation osseuse.