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Biomedical subjects

K G Heiple

Publications and source records attributed to K G Heiple.

At least 37 records · Page 2Linked to original sources
PubMed1985

Femoral shaft nonunion treated by a fluted intramedullary rod.

Twenty-five consecutive nonunions or delayed unions of the femoral shaft were treated by a fluted intramedullary rod. Fourteen patients were men; 11 were women. Sixteen fractures represented failures of closed management. Five patients had failures of primary open reduction and internal fixation. Four patients had had one attempt at operative treatment of nonunion. All but one fracture united. The one exception required a second procedure. Excellent bending and rotary fixation were achieved and union occurred promptly in most cases. Iliac crest bone grafting was not routinely required for good results. There were no major complications in this series. Two patients with severe knee extension contractures required quadricepsplasty at a later date to recover knee motion. One fracture healed with a 15 degree valgus malunion. The strength and rigidity make this device extremely reliable for the treatment of femoral shaft nonunion.

Adolescent↗
PubMed1984

Mathematical modeling and numerical solutions for functionally dependent bone remodeling.

The phenomenon of bone remodeling is a complex biological process which is dependent on genetic, hormonal, metabolic, and age-related factors as well as functional requirements. The possibility of successfully developing a mathematical model to describe and predict the adaptive response of bone to load will be significantly increased after identification of the nature of the transducer(s) which senses functional requirements and provides signals for the cellular processes responsible for bone synthesis and bone removal. In spite of the present limitations in knowledge about the functional dependence of bone remodeling, a phenomenological model has been developed that assumes that the output signal from the (as yet unspecified) transducer is a remodeling potential that can be modulated by genetic, hormonal, and metabolic factors. An attempt has been made to cast the mathematical model in such a form that the constants and variables appearing in the equations are not mere abstractions, but can be related to biological parameters. In order to use the adaptive hypothesis with specific structural model examples, a numerical procedure has been developed to determine the strain distribution, predict the remodeling (assuming that the remodeling rate is related to the strain history), and update the model by changing the geometry and material properties in response to the remodeling. This numerical procedure is repeatedly iterated to determine the structural architecture at subsequent times. The numerical approach allows use of the remodeling concepts with models of irregular geometry, inhomogeneous material distribution, and anisotropic material properties.

Adaptation, Physiological↗
PubMed1984

A computational method for stress analysis of adaptive elastic materials with a view toward applications in strain-induced bone remodeling.

A computational method has been developed to obtain numerical results in the stress analysis of adaptive elastic materials. The method is based on a 3-dimensional finite element model that can change geometry and material properties based on the local strain. The solution procedure is iterative; the model is updated in time steps based on the current remodeling to provide incremental remodeling predictions. The method provides a vehicle for examination of different continuum models and their corresponding parameters for strain-induced remodeling in long bone. Use of the method with simple models of theoretical interest is presented. Results show agreement with available analytical results as well as the importance of coupled remodeling effects not previously examined.

Adaptation, Physiological↗
PubMed1984

Improved acceptance of frozen bone allografts in genetically mismatched dogs by immunosuppression.

UNLABELLED: We studied the role of immunosuppressive therapy in improving the incorporation of frozen bone allografts exchanged across strong transplantation barriers in a canine cancellous ulnar segmental replacement model. Dogs receiving frozen bone from donors with major histocompatibility differences received one of three different immunosuppressive treatments. In two groups, azathioprine and prednisolone were administered for either twenty-eight or fifty-six days; anti-lymphocyte globulin was added for another twenty-eight-day group in a third regimen. Frozen bone was evaluated radiographically and histologically by criteria that quantified the biological characteristics of the bone itself and union between the graft and host at thirteen and twenty-six weeks after grafting. Graft incorporation in these animals was compared with graft acceptance in a similar group of untreated animals and in untreated animals in which bone was exchanged across weak transplantation barriers. Complications of immunosuppression included wound drainage, infection, weight loss, and falling white-blood-cell counts. Seven of the original thirty-seven animals died as a direct result of these complications. After twenty-six weeks the grafts in the recipients receiving immunosuppression appeared radiographically and histologically indistinguishable from those in the untreated, genetically closely matched group and from autografts. They were significantly better incorporated than identical allografts placed in untreated, genetically disparate recipients. There was no difference in the effectiveness of any of the immunosuppressive programs. CLINICAL RELEVANCE: Immunosuppression improves the biological outcome of otherwise poorly performing frozen bone allografts in dogs. This finding suggests that treatments that modify the immunological response of the host without major side effects may be useful clinically in improving the success of massive frozen bone allografts.

Animals↗
PubMed1984

Load-bearing capacity of the tibial component of the total condylar knee prosthesis. An in vitro study.

The load-bearing capability of the tibial component of total knee prostheses is affected by the coverage of the osteotomized tibial surface by the tibial component. An anthropometric study of the proximal tibia indicated that standard total condylar tibial knee components may significantly underutilize the available weight-bearing tibial surface. The unloaded area values ranged from 6% to 43% in males and from 1% to 25% in females. An experimental study of the load-bearing capability of both standard tibial components and tibial components custom-fitted to conform to the periphery of the upper tibial surface was performed. Improvement in single load to failure with the conforming prosthesis averaged 29% in females with stemless prosthesis, 21% in females with stemmed prostheses, 41% in males with stemless prostheses, and 89% in males with stemmed prostheses. Post-test examination of the failed tibiae with conforming implants indicated failure by major fragmenting of the proximal tibia rather than cancellous bone crushing, suggesting that the maximal load-bearing ability of the upper tibial surface was more nearly being achieved. The results demonstrate the benefit to be gained by fully utilizing the available tibial surface for load transmission across the joint and suggest that use of custom-fitted tibial components has considerable merit.

Anthropometry↗
PubMed1983

Comparison of growth-induced resorption and denervation-induced resorption on the release of [3H]tetracycline, 45calcium, and [3H]collagen from whole bones of growing rats.

The major effect of immobilization during growth is a smaller bone mass induced by either an increased bone resorption or a decreased bone formation. Using a method of analyzing radioisotopic loss of [3H]tetracycline and [3H]collagen from bone prelabeled in vivo, we compared the amount of bone resorption due to immobilization with bone resorption induced by growth. One hind limb was denervated in growing male rats, 6 weeks of age, that had been chronically prelabeled with [3H]tetracycline, 45calcium, and [3H]proline. The total radioactivity of the whole femur and tibia/fibula from the denervated limb was compared with that from bones of the control limb at 0, 1, 2, 4, and 8 weeks after denervation. The effect of growth on bone formation was measured by net increases in bone length, volume, and mass of matrix and mineral. Experimental bones had a significantly smaller volume and mass. Bone resorption was much greater during growth modeling than during denervation. The additional bone resorption induced by denervation was a small fraction (one-fourth) of the resorption induced by growth. Denervation during growth resulted in less bone being formed due to a smaller gain in matrix and mineral mass as a result of a reduction in bone formation.

Animals↗
PubMed1983

Contrast bone cement.

The effects of adding 1.0 cc of aqueous methylene blue dye as a visual contrast agent to a standard 40 g pack of acrylic bone cement are determined. These cements are evaluated: Simplex P (Radiopaque), Zimmer Bone Cement, and Zimmer LVC Bone Cement. Seven tests were performed. Leach out is less than 2.0% and was undetectable after day 8. Biocompatibility using a rabbit model shows contrast and white cement to be equivalent. Tension, compression, and 3- and 4-point bending strengths are not significantly altered except for a slight increase in 4-point bending strength for contrast Zimmer (regular) bone cement. Dough, set, and working times are decreased by 30-150 s. The ASTM F451 intrusion standards are met for all three contrast cements. Viscosity increases more rapidly for contrast cement, but remains sufficiently low (less than 100 N-s/m2) early after mixing to allow good penetration into bone. Ease of removal and visualization of contrast cement are shown by revision of cemented femoral total hip components in synthetic and cadaver femurs and by debriding cement particles from a soft tissue background coated with blood. The use of contrast bone cement appears to be both safe and efficacious for use in initial and revision total joint replacements. Because of the decreased working times, its use is recommended only by experienced surgeons.

Animals↗
PubMed1983

The effect of histocompatibility matching on canine frozen bone allografts.

The value of histocompatibility matching in frozen bone allografts was studied in a canine cancellous ulnar segmental-replacement model. Frozen bone that was exchanged across strong and weak transplantation barriers was evaluated histologically and radiographically at thirteen and twenty-six weeks after grafting. Histological grading criteria quantified the type of union at each end of the graft and the degree of remodeling of the marrow, spongiosa, and compacta. Radiographic grading criteria included the presence of union at each end of the graft and the degree of remodeling of the graft segment. In vitro studies for serum antibody and cell-mediated immunity were carried out by isotopic cytotoxicity methods at seven intervals during the twenty-six-week study period. Histologically, the strong-barrier allografts had fewer osseous unions and less reorganization of spongiosa and marrow when compared with autograft controls at both thirteen and twenty-six weeks. Radiographically, the strong-barrier allografts at thirteen weeks had fewer unions and marked resorption of grafts material when compared with autograft controls. There were no differences between weak transplantation-barrier grafts and control autografts radiographically or histologically at thirteen and twenty-six weeks after grafting. Frozen bone allografts did not elicit detectable serum antibody or lymphocytes that were cytotoxic for donor cells.

Animals↗
PubMed1983

Experimental hemijoint and whole-joint transplantation.

Technically perfect autologous hemijoint transplants maintain biologic viability, although gradual deterioration of the joint surface may occur with the passage of long periods. Allogeneic transplants demonstrate varying degrees of degeneration, depending on the circumstances surrounding the procedure. Fresh allografts with a large amount of subchondral bone are rapidly rejected, with an immune response directed against both bony and cartilaginous components. Frozen allografts with a small amount of subchondral bone usually maintain the overall joint configuration for some time but then degenerate. In many instances the role of the immune system in rejection of joint transplants is difficult to define. The fate of whole nonvascularized knee joint transplants is comparable with that of hemitransplants. Although fresh autografts give the best results, the subchondral bone can collapse, and articular cartilage degenerates in some cases. Recent investigations of immediately revascularized canine whole knee transplants show that when the blood supply is maintained to the autograft, normal biologic function is sustained for as long as five years after grafting. When appropriate immunosuppression is used, successfully revascularized allografts survived for as long as 18 months. However, bony and cartilaginous necrosis occurs in focal areas. In any case, successfully revascularized osteochondral grafts are biologically superior to nonvascularized grafts.

Animals↗
PubMed1983

Ankle arthrodesis by chevron fusion with internal fixation and bone-grafting.

We evaluated the results in thirteen patients with disabling tibiotalar arthritis who underwent a new operation for ankle fusion for relief of pain. The procedure in all of these patients was a chevron (pitched-roof) tibiotalar osteotomy and excision of the joint. A bilateral approach to the ankle joint was used and the arthrodesis was supplemented by internal fixation and a tibial onlay graft applied medially. There were few complications, none of them of major importance. The after-care required only immobilization in a short cast. All but one patient had a solid fusion. The final result was a normal-looking ankle with good function.

Adolescent↗
PubMed1982

Fractures in the first year of life. A diagnostic dilemma.

Thirty-four patients with 55 fractures in the first year of life were studied. There were 189 patients with 21 skull fractures and 16 patients with 19 extremity fractures. Extremity fractures occurred at a significantly younger age than did skull fractures. Cause was defined as accidental in 15 patients (44%) and nonaccidental (child abuse) in 19 patients (56%), representing a greater incidence of accidental cause than previous reports indicated in this age group. There were no significant differences between the two groups with regard to mean age, percentage of girls, number of fractures per patient, and distribution of fractures. Eight patients had notable constitutional abnormalities contributing to the causes of their fractures. There was no difference between this group and normal patients with regard to mean age, percentage of girls, distribution of fractures, and number of fractures per patient.

Accidents, Home↗
PubMed1982

The material properties of immature bone.

The age-related material properties of developing immature canine bone were determined for the femora, tibiae, humeri, radii, and ulnae in animals from 1 wk of age to maturity. These properties included bone geometry changes, material tissue properties, and qualitative and quantitative morphological evaluations. All bones exhibited a two-phase growth cycle, an initial rapid phase (20 wk) followed by a substantially slower growth to maturation (48 wk). All properties showed age-related changes except bone tissue strain to failure.

Age Factors↗
PubMed1982

Isotopic evidence for resorption of soft tissues and bone in immobilized dogs.

UNLABELLED: Various experimental methods for producing bone and ligament atrophy have yielded contradictory results. These methods include denervation, immobilization (both internal and external), and disarticulation. We studied a model of internal skeletal fixation for twelve weeks in dogs that were chronically prelabeled with 3H-tetracycline, 45Ca, and 3H-proline. Bone resorption was analyzed by the loss of 3H-tetracycline, and bone and soft-tissue mass were analyzed by the radiochemical and chemical analysis of calcium and collagen. The strength of the anterior cruciate ligament was studied in tension to failure when a fast rate of deformation was applied. Failure of the femur-ligament-tibia complex occurred through the insertion of the ligament into the tibia for both the experimental and the control limbs. Loss of collagen was greater in the tibia and femur than in the lateral meniscus and anterior cruciate ligament, and correlated with a mechanical failure via bone. No evidence for collagen replacement in atrophied tissues was found, but one-half of the resorbed calcium was conserved. The marked loss of 3H-tetracycline indicated that bone atrophy was the result of increased resorption of bone rather than decreased bone formation. CLINICAL RELEVANCE: We have demonstrated significant atrophy of the soft tissues (lateral meniscus and anterior cruciate ligament) as well as of bone in immobilized joints of dogs. It is likely that the decrease in strength of the bone-ligament-bone complex is related to this atrophy of soft tissues and bone around the joint.

Animals↗
PubMed1981

Structural properties of immature canine bone.

Structural properties of growing canine long bones were determined from three and four-point bending tests. Mechanical and geometric properties were found to follow a biphasic growth process, with a rapid increase in bending strength and moment of inertia from l to 24 wk of age and a substantially decreased rate thereafter to maturity. Predicted bone tissue material properties were also found to follow this biphasic developmental process.

Age Factors↗
PubMed1981

Total knee arthroplasty in classic hemophilia.

Thirteen total knee replacements of the semiconstrained type were performed in ten patients with classic hemophilia (factor-VIII deficiency) and followed for two to six and one-half years. The average age at operation was twenty-seven years. Preoperatively, all patients complained of severe pain and were markedly disabled: five required wheelchairs and five needed crutches to walk. All patients had declared themselves willing to accept arthrodesis as the only surgical alternative. The results of the total knee arthroplasties, as determined by a standard knee-scoring system, were four knees rated as excellent or good and eight rated as fair. The thirteenth knee required an arthrodesis after a deep infection and was rated as a failure. Pain and function were markedly improved, and no patient required a wheelchair postoperatively. Although the postoperative knee motion was only slightly improved, it was in a range that meant a more functional knee. Postoperative complications included intra-articular or intramuscular bleeding in three patients and one posterior tibial and three peroneal-nerve palsies, one of which still was not completely resolved at the time of writing. Total knee arthroplasty in hemophilia appears to be a satisfactory procedure for reconstruction of the severely damaged knee when arthrodesis is the only other acceptable alternative.

Adolescent↗
PubMed1979

A fluted intramedullary rod for subtrochanteric fractures.

A new intramedullary rod has been developed for the treatment of subtrochanteric fractures. The stepped fluted rod is designed as a single unit and has exceptional bending strength and rigidity as well as excellent torsional load-carrying capacity. It has been used successfully in eighteen patients with a variety of subtrochanteric fractures. Union was achieved in all instances and no failure of the implant occurred. The simplified technique of insertion, the strength of the device, and the results of this study indicate that the fluted subtrochanteric rod has several advantages over other available devices.

Adult↗