Search PubMed⌕ Search

Biomedical subjects

H U Cameron

Publications and source records attributed to H U Cameron.

At least 109 records · Page 6Linked to original sources
PubMed1982

Total hip revision arthroplasty: does sepsis influence the results?

The results of revision total hip arthroplasty, with or without sepsis, are compared in a review of the recent literature. In 661 total hip revisions without sepsis, there is an overall 54% excellent/good/satisfactory rate and a 12% infection rate. Of 1063 total hip revisions in the presence of or after sepsis, there is an overall success rate of 73% and a 17% reinfection rate. Comparison of the two groups is difficult due to the different criteria used to diagnose infection, the variable use of parenteral antibiotics and cement impregnated with antibiotics, the frequently short follow-up periods, and the definition of success by different rating s stems. Aside from infection, before advising revision surgery or excision arthroplasty, consideration should be given to the individual patient, the hip to be revised, and the technical skills available. Follow-up should be monitored yearly by an independent examination of the patient, not by chart review or telephone questionnaire. Standardized rating methods should be used, together with strict criteria for the diagnosis of infection. Only in this way will results from different centers be comparable.

Bacterial Infections↗
PubMed1981

A study of bone remodeling using metal-polymer laminates.

Bone remodeling due to stress-shielding has been studied using a model system consisting of metal-polymer laminated fixation plates securely fixed to canine femurs. The plate stiffness was controlled by varying the ratio of metal facing to polymer core thickness in the laminate design while secure fixation to bone was achieved by providing a porous bone interfacing surface for the ingrowth of bone from the periosteal surface. Observations of laterally and medially placed plates indicated resorption in the area of the periosteal and endosteal bone surfaces respectively, for the higher stiffness composite plates used. The results indicate that plate stiffness greater than approximately 70 GPa (axial) and 6 N m2 (flexural) will result in extensive bone remodeling in the canine femur after a six month implantation period.

Alloys↗
PubMed1981

Mechanical failure modes in total knee replacement.

In an attempt to define failure modes, a study of 39 knees which failed mechanically has been carried out. In 7 cases failure occurred on the femoral side and in 32 on the tibial side. There was fracture of one femoral component. All femoral loosenings and/or sinkage occurred in malaligned components. Two main tibial failure modes were noted, lateral subluxation of the tibia on the femur leading to loosening and sinkage of the tibial component. Release of popliteus prevents lateral subluxation. Correct component alignment and the use of a large area tibial component resting on the cortices should decrease the incidence of tibial sinkage.

Biomechanical Phenomena↗
PubMed1981

Essential design considerations for microporous implants: preliminary communication.

The introduction of microporous metallic implants into which bone can grow to stabilize the implant has necessitated considerable work prior to clinical studies. Ten years of bench and animal testing have resulted in a clinically available prosthesis with a multilayer porous coating with a pore size of 50-300 mu. Initial clinical trials with a 50-100 mu hip prosthesis indicated the necessity to increase the pore size to 300 mu and clinical studies of such prostheses are at present underway.

Animals↗
PubMed1981

Osteogenic phenomena across endosteal bone-implant spaces with porous surfaced intramedullary implants.

Porous surfaced femoral components of hip prostheses stabilized by tissue ingrowth are often situated a certain distance away from the endosteal cortex in the diaphysis. The purpose of this study was to examine the significance of this space between an implant and the cortex on bone growth into the porous surface of the implant. Intramedullary rods of different diameters with porous surface regions made of powder metal were inserted into the femurs of adult beagles. The rods had outside diameters of 2.5, 3.2, 4.5, and 5.5 millimeters; this variation produced endosteal bone-implant surface spaces ranging from 0 to 4 millimeters. The animals were sacrificed at 4, 8, 12, and 16 weeks. Histological sections revealed that by 12 weeks the implants became generally surrounded by a thin shell of spongy bone which was joined to the endosteal cortex by bony trabeculae. This feature was most prominent for implants which were approximately 2 millimeters or less from the endosteum. Denser, more haversian-like bone developed up to and within those areas of implants which were in contact with the cortex. The development of this intramedullary type of bone could significantly contribute to the fixation strength of clinical porous surfaced prostheses whose stems do not completely fill the medulla.

Alloys↗
PubMed1981

Radiographic and morphologic studies of load-bearing porous-surfaced structured implants.

Load-bearing porous-surfaced implants in dogs which failed were not incorporated by bone ingrowth. The implants were incorporated only by fibrous tissue ingrowth. Collagen fiber orientation within this fibrous tissue and Sharpey's fiber-like features at the interface between the fibrous tissue and a surrounding layer of dense bone suggest the adequacy of the fibrous tissue attachment for support of a loaded implant. The surrounding dense bone layer could be distinguished radiographically within three months of the operation. This radiopaque line is similar to that observed around some porous surfaced hip implants in humans. Observations of animal mobility up to six months postoperatively suggest that fibrous connective tissue growth into porous implants can provide adequate mechanical support for weight-bearing dogs.

Animals↗
PubMed1981

Revision of total knee replacement.

In the London and Toronto areas between 1969 and 1978, 597 patients had 661 cemented knee replacements. Eighty-nine (13.5%) prostheses failed; 73 of them were revised. Nineteen (2.9%) failed primarily because of infection. The revised replacements were examined and rated using a modification of the British rating system. The overall results of revision were excellent or good in 30% and fair or poor in 52%. Fusion was attempted in two patients after revision. In 16 patients with failed replacements that were not revised, fusion was attempted in 9; 4 of the 16 patients had amputation. The results of failure in knee replacement surgery are similar to those of hip replacement, but are helped considerably by lower patient expectation.

Aged↗
PubMed1981

Unicompartmental knee replacement.

The results of unicompartmental knee replacement in a series of 83 knees were reviewed for the period of 1970 to 1978; 30.1 percent achieved good or excellent results; 48.2 percent fair or poor results; 21.7 percent were failures. The vast majority of failures and poor results were due to technical errors. Only 9.6 percent of the nonoperated contralateral compartments required further surgery.

Aged↗
PubMed1980

Review of a failed knee replacement and some observations on the design of a knee resurfacing prosthesis.

In a review of failed knee replacements, one design was found to have a seventy-three percent failure rate at three years. In this design the tibial component resembled the MacIntosh prosthesis and the femoral component was polyester. Failure in most cases resulted from generation of wear debris resulting in a severe synovitis and loosening of the femoral component. These findings suggest that the femoral component should be metal and the tibial component plastic, and that if the tibial component is backed with metal, in most cases it need not be cemented in place.

Humans↗
PubMed1980

The effect of porous surface configuration on the tensile strength of fixation of implants by bone ingrowth.

In an attempt to gain information that could be directly applied to the design of clinical porous-surfaced prostheses intended for biological attachment by bone ingrowth, the tensile strength of the bone-implant interface was expressed as a function of 2 fundamentally different porous-surface configurations. Using powder metallurgy techniques, standard 3-hole fracture fixation plates were prepared with both a single and a multiple layer of spherically shaped metal powder particles on the bone-contacting surface to produce implants with different porous surfaces. These plates were implanted onto the lateral aspect of canine femurs for periods of 4, 6, 8, 12, 18, and 24 weeks. Mechanical tests were performed to measure the tensile strength of fixation of the implants by the ingrowth of bone. The results of the mechanical tests indicated that implants with the multiple particle layer surfce configuration develop a greater tensile strength of fixation than do implants with the single particle layer surface configuration. In addition, this fixation strength develops more quickly if the cortical bone is petaled prior to implantation. These findings should be considered when designing porous-surfaced implants intended for fixation by bone ingrowth.

Animals↗
PubMed1979

Femoral neck fractures following surface replacement.

A femoral neck fracture following surface replacement of the hip has been studied and five potential causes of failure were noted. These consisted of; removal of a hip nail during surgery, use of a too small femoral cup, initial reaming in varus, notching of the femoral neck, and failure to completely seat the cup.

Female↗
PubMed1979

Bone ingrowth and stress shielding with a porous surface coated fracture fixation plate.

The extent of bone remodelling under metal fixation plates attached to bone by (i) normal screw fixation and (ii) bone ingrowth into a porous metallic surface underlayer sintered to the metal plate was investigated. Extensive bone remodelling was observed under the integrally bonded porous surface layered plate. This remodelling could be attributed to the more extensive stress transfer from bone to metal plate because of the good bone-to-implant bonding. The importance of stress shielding with high stiffness implants is demonstrated.

Alloys↗
PubMed1979

Dislocation requiring revision in total hip arthroplasty.

In a study of 141 hip revisions seventeen were found to be due to recurrent dislocation. Thirteen cases occurred immediately postoperatively and four more than two years following surgery. In the early cases component malposition was found to be the commonest cause of dislocation. Revision resulted in only 40% acceptable results.

Hip Dislocation↗
PubMed1979

The results of revision of total hip arthroplasty.

The results of 140 total hip revision procedures for "non-septic" loosening, dislocation, and fracture of the femoral stem or shaft have been personally reviewed and rated by the Harris method. The minimum follow-up period was six months: thirty-three (24 per cent) showed excellent or good results, seventy-two (51 per cent) showed fair or poor results. Subsequent excision arthroplasty was performed in thirty-one patients. The infection rate for these revision procedures was very high, suggesting that many were already infected at the time of revision, and that every "loose" hip must be assumed to be infected until proved otherwise. The mortality rate of 3 per cent was surprisingly low after more than one major surgical procedure in these elderly patients.

Aged↗
PubMed1978

Femoral neck fractures in osteoarthritis of the hip.

Femoral neck fractures seldom occur in hips with a significant degree of osteoarthritis. Experience with three hitherto undescribed fractures around hip nails suggests that the ridge of new bone which forms on the inferior part of the femoral neck in osteoarthritis increases the strength of the neck, thus decreasing the tendency to neck fractures.

Aged↗