Biomedical subjects
H U Cameron
Publications and source records attributed to H U Cameron.
Loosening of the femoral component in surface replacement of the knee.
The incidence of loosening of the femoral component of the ICLH knee has been found to be lower than that of the tibial component. This is thought to be due to the fact that the compressive strength of the distal femur has been found to be greater than that of the proximal tibia. It has further been shown that the strength of even the femur can be so reduced by the osteoporosis accompanying Rheumatoid Arthritis that it becomes insufficient for adequate prosthetic fixation.
A porous metal system for joint replacement surgery.
A porous coated chrome cobalt system has been developed to provide long term stabilization in joint replacement surgery. The pore sizes are 50 to 100 microns, thus ensuring sufficient fatigue strength for use in high load bearing situations. Extensive in vitro and in vivo studies have been performed, and a five year follow-up of porous coated total shoulder prostheses has failed to reveal any evidence of loosening. The early results of porous coated hip implants is encouraging.
Evaluation of biodegradable ceramic.
An evaluation of a porous biodegradable ceramic, tricalcium phosphate, has been carried out. When implanted in cancellous bone, it is rapidly infiltrated with bone and slowly resorbed. When held rigidly against raw, bleeding, cortical bone, again rapid bone ingrowth occurs. The material does not give rise to any untoward tissue reaction, nor does it cause any systemic reaction. It can therefore be concluded that the material is safe for use in clinical practice, and can be used in specific instances either to replace or to supplement bone grafting.
Degenerative osteoarthritis associated with osteopetrosis.
A case of osteopetrosis has been described in which bilateral osteoarthritis of the hips occurred before the age of 40. As the osteoarthritis was not explicable on the bases of deformity it was considered that osteoprtrosis might be the etiological factor. Further circumstantial evidence for this causal relationship has been found in a review of the literature.
The rate of bone ingrowth into porous metal.
Experiments have been devised to study the rate of ingrowth of bone into porous metal with pore sizes up to 100 mu and to study the significance of a gap between the porous metal surface and bone. When the porous coat was in direct apposition with bone, the implant was firmly locked in place after a three week period and the plateau value of implant-tissue shear strength was reached at four weeks. A gap of 1.5 mm between the bone and the implant was bridged by new bone within four weeks.
The bone-metal interface following hip nailing.
In order to establish a base line for tissue reaction in relationship to loaded implanted foreign materials that might be used for comparison with new materials, the interface between the trabecular bone in the femoral head and hip nails has been studied in 20 specimens. The interface consists of four distinguishable layers: a cellular layer at the surface, a layer of fibrovascular connective tissue, a layer of collagenous connective tissue and/or fibrocartilage, and a peri-implant bone plate. Even 10 years after insertion of the nail this interface remained cellularly active, the activity presumably being related to the different modulus of elasticity between the metal and the surrounding trabecular bone.
Carbon fiber-reinforced bone cement in orthopedic surgery.
A tougher, more fatigue-resistant bone cement consisting of short, highmodulus carbon fibers dispersed randomly in normal ply(methyl methacrylate) bone cement has been developed. Fatigue and impact tests are reported that demonstrate the superior fracture resistance and prolonged load-carrying ability of this system. The use of this carbon fiber-reinforced bone cement in the treatment of a pathological fracture of the femur associated with neoplastic disease of the bone is reported. The tougher cement has provided long-term stability of the fracture.
Torsion of a tumor within the suprapatellar pouch. Report of a case.
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The femoral stem/cement interface in total hip replacement.
A study of the cement prosthesis interface has been carried out on the femoral component of 5 total hip relacements which had been in place between 7 weeks and 5 years. In every case a thin layer of connective tissue at varying stages of organization was present between the prosthesis and the cement. This suggests that the prosthesis is not rigidly fixed to the cement and is capable of micromovement. The gap presumably comes about by a combination of factors which include thermal expansion of the femoral stem, shrinkage of the cement and organization of the film of blood or tissue fluid present on the stem at the time of implantation. This information must be used when construction mathematical models of joint replacements, but its clinical significance is not yet fully clear.
Ischemia associated with the Charnley anterior approach to the ankle. Report of two cases.
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Pyrophosphate arthropathy.
A scanning electron microscopic study of six cases of pyrophosphate arthropathy has been conducted. In the majority of cases the crystals were rectangular. In some cases giant crystals were present. In one case, the crystals were pyramidal. It is concluded that many geometrically different forms of calcium pyrophosphate crystal exist and that the scanning electron microscope is a useful tool in the differentiation of pyrophosphate arthropathy from other forms of crystal synovitis.
Observations on osteoarthritis of the hip joint.
A correlation of the X-ray changes with the pathological changes seen in arthritic hips obtained at surgery or from cadavers, reveals 6 different patterns of osteoarthritis of the hip. The study suggests that the pathogenesis of the degenerative changes is different in each type and as such, would influence the results obtained by surgical intervention.
The microhardness of articular cartilage.
The standard metallurgical technique of microhardness testing was useful for investigations on the physical properties of articular cartilage. The problem of visco-elasticity of the cartilage was overcome by using a brittle lacquer coating as a memory device. The surface layer was the hardest plane when the superficial layer was intact. Removal of the superficial layer however, made this plane the softest. There was no variation in hardness with depth. The plane at right angles to the vector of movement of the joint was harder than the plane parallel to the vector of movement. This indicates the presence of a secondary fiber system in the middle layer of articular cartilage. The fibers in this system run predominantly at right angles to the direction of motion of the joint.
Trabecular stress fractures.
This study was conducted to evaluate the theory that increased rigidity in the subchondral cancellous bone and trabecular stress fractures are responsible for the development of osteoarthritis. Histological sections of the entire femoral head were examined in 80 normals, 50 cases with early degenerative changes, and 50 cases with advanced osteoarthritis. It was found that trabecular stress fractures occur normally and show no greater incidence in early osteoarthritis. Increase in thickness of the trabeculae not associated with fractures is seen, but only after considerable cartilage disruption. It is concluded that trabecular stress fractures are not of importance in the development of osteoarthritis.
A radiologic sign of lateral subluxation of the distal tibial epiphyses.
Linear calcification of the interosseus membrane at the ankle in a juvenile who has sustained an eversion/abduction injury with otherwise normal radiographs indicates that a Type I injury has occurred to the distal tibial and fibular epiphyses, with displacement at the time of injury. This is a significant injury with the potential to cause growth arrest of the tibial epiphyseal plate.
Techniques of closed bone biopsy.
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