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Biomedical subjects

E L Radin

Publications and source records attributed to E L Radin.

At least 55 records · Page 3Linked to original sources
PubMed1986

Comparison of joint degeneration models. Surgical instability and repetitive impulsive loading.

We used surgical instability and repetitive impulsive loading in rabbits to initiate degenerative changes in knee joints. Synovial membrane and cartilage samples were examined by light and electron microscopy. Early synovial inflammation at three days postoperatively preceded cartilage destruction in the instability model. Synovial inflammation was only apparent after eight weeks in the loading model and increased subsequently to cartilage destruction. Cartilage breakdown was focal and limited to the weight-bearing area. Comparison of the histological data of the two arthrosis models suggests that different inductive mechanisms may be involved in cartilage degeneration, but in both models the inflammatory changes appeared to be secondary to mechanical factors.

Animals↗
PubMed1986

Anterior tibial tubercle elevation in the young adult.

A modification of Maquet's procedure, longitudinal proximal tibial osteotomy, was performed on 36 adults under the age of 40. The tibial tubercle was elevated between 2.0 and 2.5 cm. Fourteen were operated on for significant osteochondral injury to the underside of the patella, including patellar fracture; 16 were operated on because of osteoarthrotic change in the patellofemoral joint secondary to recurrent subluxation. Six were operated on because of pain persisting after previous patellectomy. Follow-up ranged between 2 and 5 years, was at least 2 years, and averaged 3.53 years. A good result was determined to be one in which the patient had no pain requiring medication or activity limitation; a poor result was designated when the patient had pain requiring medication or activity limitation. The success rate among the trauma or fracture group was 94 per cent, among the subluxation group 88 per cent, and among the postpatellectomy group 66 per cent. Failures included unrecognized osteoarthrosis of the tibiofemoral joint, psychiatric problems, a reflex sympathetic dystrophy, a compensation neurosis, a failure to correct excessive knee valgus with recurrent subluxation, and a fall displacing the operation. Serious complications, osteomyelitis and a displaced graft resulting from a postoperative fall, occurred at a rate of 5 per cent; minor complications, tenuous skin healing and tibial tubercle shingle fractures, occurred at a rate of 19 per cent. This operation is indicated only for patients with osteoarthrosis of the patellofemoral joint and is contraindicated in the presence of tibiofemoral osteoarthrosis. High success rates are attributed to careful attention to indications and contraindications and to the design and details of performing the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Fatigue fracture of a forearm plate within a long-arm cast.

Open fractures of both left ulna and radius, in which a segment of the radius was found to be missing, occurred in a 27-year-old man. The fractures were treated by open reduction, internal fixation with ASIF semitubular plates, and bone graft. Because of slow radiological union, regrafting was required twice. Approximately six months after the third operation, roentgenograms showed that the bone plate was broken, even though the fractures had been protected in a long-arm cast. The fatigue fracture of the plate, positioned on the posterior surface of the ulna, was presumably caused by the force of the finger flexors, most of which originate above the fracture site, and which were still able to contract because the fingers were not immobilized.

Adult↗
PubMed1986

The Maquet procedure--anterior displacement of the tibial tubercle. Indications, contraindications, and precautions.

Maquet recommended 2-2.5 cm of anterior tibial tubercle elevation for patients with symptomatic osteoarthrosis of the patellofemoral joint. Fifty-three patients with osteoarthrosis were divided into three groups. The first 12 patients were treated by the classical Maquet procedure; 11 were totally relieved of patellofemoral pain, but there was one failure and five complications. In the second group of 32 patients, the patella was realigned within its groove to alter tracking of the patella to the proximal femoral condyles when necessary. Fish-mouthing technique and insertion of a drain after surgery were done. After a two-year follow-up examination, there were two failures and five complications. A third group of nine patients was treated with Ferguson's modification of Maquet's operation using a 1.25-cm tibial tubercle elevation through a transverse incision; two of the nine had complications, subsequently treated successfully by converting Ferguson's operation into the Maquet operation, as modified for Group II. The modified Maquet procedure can be an effective and reliable treatment of patellofemoral arthrosis with a relatively low incidence of complications.

Adolescent↗
PubMed1986

Role of subchondral bone in the initiation and progression of cartilage damage.

Osteoarthrosis is a physiologic imbalance, a "joint failure" similar to "heart failure," in which mechanical factors play a role. The initiation and progression of cartilage damage are distinct phenomena. One of the mechanisms of initiation may be a steep stiffness gradient in the underlying subchondral bone. Progression of cartilage lesions probably requires stiffened subchondral bone. In such situations, transverse stresses at the base of the articular cartilage could cause deep horizontal splits in that tissue. The most likely cause of subchondral stiffening in an otherwise congruent joint is repeated failure of the musculoskeletal peak dynamic force attenuation mechanisms. The health and integrity of the overlying articular cartilage depends on the mechanical properties of its bony bed. In certain models of osteoarthrosis, alterations of the bony bed occur before the cartilage changes and suggest that this can occur in clinical conditions. Stiffening of the subchondral bone also can effect joint conformation, which involves deformation of articular cartilage and bone to create maximum contact areas under load.

Animals↗
PubMed1985

Bone remodeling in response to in vivo fatigue microdamage.

It has been suggested that osteonal remodeling is triggered by bone microdamage. The validity of this theory rests on the assumption that loading within the physiological range will produce substantial microdamage with relatively few load cycles. The object of the first experiment was to determine threshold values required to consistently produce fatigue microdamage in vivo. The left forelimb of five groups of dogs, characterized by different strain levels and different numbers of load cycles, were loaded in three point bending. The number of microscopic fields which contained some microdamage was calculated as a percentage of the total number of fields. This experiment indicated that loads producing strains as low as 1500 microstrain on the radius and 1400 microstrain on the ulna for 10,000 cycles will produce significant bone microdamage. A second experiment was performed to verify this threshold and to determine whether microcracks are associated with the initiation of bone remodeling. Procedures in this experiment were the same as those in the first, except that all dogs were loaded in such a way as to produce strains on the radius of 1500 microstrain for 10,000 cycles, and the dogs were sacrificed 1-4 days after loading. The loaded limb demonstrated significantly more microdamage than the control limb (p = 0.03). Moreover, we observed 44 times as many microcracks in association with resorption spaces as expected by chance alone. These data support the hypothesis that fatigue microdamage is a significant factor in the initiation of intracortical bone remodeling.

Animals↗
PubMed1984

Effects of mechanical loading on the tissues of the rabbit knee.

We studied changes in subchondral bone and articular cartilage in an animal model of osteoarthrosis. In this model we applied repetitive impulsive loads to rabbits' knees. Their legs were held in short leg splints so the rabbits were unable to dampen the peak applied load with ankle flexion. After sacrifice, at 1 day to 6 weeks, we studied proximal tibial load-bearing cartilage histologically, biochemically, and with radioactive sulfate uptake. We also studied the subchondral bone under that cartilage histologically, histomorphometrically, with bone scan (99mTc pyrophosphate), and by tetracycline labeling. An increase in 99mTc labeling of the subchondral bone was the first reliable change observed. This was followed by an increase in tetracycline labeling, bone formation, and a decrease in porosity, which has been associated with relative stiffening of bone. Horizontal splitting and deep fibrillation of the overlying articular cartilage followed the early bone changes. All of these changes preceded changes in content and characterization of cartilage proteoglycans or increased chondrocyte activity as manifested by incorporation of radioactive sulfate. In this model the early bone changes preceded changes in the articular cartilage. The deep splitting of articular cartilage occurred prior to metabolic alteration of that tissue.

Animals↗
PubMed1984

The effects of exercise on the bones of postmenopausal women.

The effects of walking and aerobic dancing on the bones of 73 recently postmenopausal women have been compared by photon absorptiometry of the distal radius with a control group who did not exercise. The period of observation was six months. Results showed that the control group and the walking group lost statistically significant amounts of bone mineral content (1.6%, and 1.7% respectively), but that the dancing group did not (0.8%). The control group did not show a significant increase in the bone width (0.9%), but both the dancing (1.3%) and walking (1.6%) groups did. Changes in the cross-sectional moment of inertia of the radius were estimated for each subject based on bone mineral content and bone width values. Both exercise groups experienced significant increases in this variable, while the control group did not. Plasma oestrogen levels were not influenced by exercise. The results support the hypothesis that mechanical loading due to exercise may be effective in preventing postmenopausal osteoporosis.

Biomechanical Phenomena↗
PubMed1984

Finite element studies of some juxtarticular stress changes due to localized subchondral stiffening.

A finite element analysis was undertaken in concert with an animal model of mechanically-induced osteoarthritis. The numerical model was used to explore stress transmission anomalies associated with localized subchondral stiffening due to implantation of small cylindrical plugs immediately below the subchondral plate of sheep. The quasi-static, plane strain computational formulation included solution of the non-linear intra-articular contact problem, and was validated by comparison with a corresponding analytical solution and with the in vivo experimental results. The numerical results showed that stress aberrations due to metal implant insertion were felt most greatly in the bone immediately surrounding the implant, but that nominal compressive stress elevations up to about 50% could also be induced in the overlying deep hyaline cartilage layer. This localized cartilage stress elevation following the insertion of a metal plug could be seriously affected by a number of factors, including the positioning of the implant, variation in the area of intra-articular contact, or the elastic modulus of the cancellous bone and/or subchondral plate. Experimentally-observed fibrous encapsulation also reduced the cartilage stress elevation effect, but later bony remodelling and the development of a corticalized shell around the implant encapsulation served to re-elevate the local cartilage stresses.

Animals↗
PubMed1984

Architectural changes in the proximal femur following prosthetic insertion: preliminary observations of an animal model.

A study was made of the changes occurring in the proximal femur following unilateral total hip replacement in fourteen sheep. Implants were observed 0-12 months post-operatively. Contralateral implants inserted at sacrifice served as controls. The paired specimens were cut into five transverse sections and stereologically analyzed. The following phenomena were seen during the post-operative year: (a) calcar resorption; (b) encapsulation of the prosthetic cement in fibrous sheath; (c) interruption of the trabecular network between the cement-stem system and the cortex; (d) increase in the cross-sectional moment of inertia of the cortical shell. These changes form a consistent pattern of biological responses to the implant, the details of which are important because they suggest failure mechanisms and demonstrate the inadequacy of simple analytical models based on static pictures of the bone-implant composite structure. Failure modes may depend on the initial degree of bone-cement interdigitation. Concentric layers of fibrous tissue surrounded by layers of dense bone were formed where interdigitation was not extensive. Where interdigitation was maximal, a band of bony resorption separated the cement-bone complex from the endosteal trabecular bone. Increased levels of bone-cement interdigitation would not appear to influence the ultimate outcome, but, rather, only the mode of failure of the prosthetic attachment.

Animals↗
PubMed1984

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.

Cartilage, Articular↗
PubMed1984

Role of the menisci in the distribution of stress in the knee.

Photoelastic studies were performed to compare the effects of meniscectomy, longitudinal meniscal tear, and retention of the meniscal rim on the magnitude and distribution of the stresses in the medial compartment of the knee. The results are consistent with the concepts that the meniscus protects the articular cartilage of the knee from stress concentrations and that retention of a torn, undisplaced meniscus or the presence of an outer meniscal rim are preferable to the absence of the meniscus.

Elasticity↗
PubMed1983

Osteoarthrosis: sex-specific relationship to osteoporosis.

Examination of an Eskimo skeletal series demonstrated at least two etiologically distinct groups of joint deterioration divided along sex lines. Low bone mineral content (BMC) among women and high BMC among men were associated with osteoarthrosis on the tibial plateau. This finding contradicts conventional wisdom based on clinical observation, which suggests that reduced skeletal mass prevents osteoarthrosis.

Adult↗
PubMed1983

Tarsal tunnel syndrome.

In 14 patients tarsal tunnel syndrome was associated with varus heels and pronated, splayed forefeet. Review of the literature and the author's experience suggest that these conditions may be a common cause of the tarsal tunnel syndrome. Treatment of fixed varus deformities of the heel by outer heel wedges has been shown to be ineffective. Although outer heel wedges provide symptomatic relief in patients with relatively flexible hindfeet, surgical release of the flexor retinaculum behind the medial malleolus is the treatment of choice in patients who have the tarsal tunnel syndrome with planovarus deformity and is successful in more than 90% of cases. The tarsal tunnel syndrome, in the author's experience, is grossly underdiagnosed. Tarsal tunnel syndrome should be suspected in patients who have pain in the bottom of the feet without localized forefoot tenderness, who have a varus heel and a pronated, splayed forefoot, and who have a positive Tinel's sign behind the medial malleolus. It is important to differentiate tarsal tunnel syndrome from a peripheral neuropathy that obviously will not respond to surgical intervention.

Adult↗
PubMed1982

Factors influencing articular cartilage wear in vitro.

The in vitro wear of articular cartilage in oscillating and impulsively loaded bovine metatarsophalangeal joints was studied. Articular cartilage scarification had little effect on cartilage wear, but stiffening of the subchondral bone with methyl methacrylate greatly increased the rate of cartilage loss, whether or not it had previously been scarified. Glutaraldehyde treatment of articular cartilage for 30 minutes decreased is wear rate. Guanidinium chloride extraction of the cartilage before wear testing caused it to peel off its subchondral bed. This effect could be spared by prior glutaraldehyde fixation.

Aging↗
PubMed1982

Effect of prolonged walking on concrete on the knees of sheep.

Adult sheep were subjected to prolonged activity on hard surfaces by walking them daily on concrete and housing them on tarmac. Control sheep were walked on compliant wood chip surfaces and pastured. After two and a half years significant changes were seen in both the distal femoral articular cartilage and subchondral trabecular bone of the knee joints of the hard surface walkers. The hexosamine content of the articular cartilage in the hard surface walkers was lower and this decrease was more marked in the weight-bearing than in the non-weight-bearing areas of the knee. The trabecular pattern of the subchondral bone became significantly altered, with a marked change in trabecular structure acting to stiffen the tibio-femoral joint at th expense of the patello-femoral articulation. There was a substantial increase in the contiguity ratio of bone in the tibio-femoral area. The cortical thickness of the subchondral plate was increased in both the tibio-femoral and patello-femoral areas. We concluded that significant changes occur in both cartilage and bone as a result of prolonged walking on hard surfaces.

Animals↗