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Biomedical subjects

F R Convery

Publications and source records attributed to F R Convery.

At least 19 recordsLinked to original sources
PubMed1995

Effect of tissue culture storage on the in vivo survival of canine osteochondral allografts.

In vitro studies in our laboratory have shown that the biomechanical and biochemical characteristics of osteochondral grafts can be preserved for as long as 28 days under tissue culture conditions. This study represents an attempt to extend these results to an in vivo model. In adult mongrel dogs, either an autograft, a fresh allograft, or a stored allograft was placed in a standardized defect on the weight-bearing surface of the medial femoral condyle. The stored grafts were kept at 4 degrees C in tissue culture medium for 14 days prior to implantation. The animals were killed at 12 weeks. Cartilage from the contralateral knee served as a control. The modulus and permeability of the cartilage were assessed with confined compression creep tests. The collagen and glycosaminoglycan contents were measured, and the cartilage was analyzed histologically with hematoxylin and eosin and safranin O stains. Grossly, the cartilage appeared viable at harvest. The histologic results were similar in the treatment groups, with the same spectrum of mild degenerative changes being noted in each group. The glycosaminoglycan content was significantly less in the autograft group than in its control group and than in the fresh allograft group. The glycosaminoglycan content did not differ significantly between fresh and stored allografts. The collagen content, modulus, and permeability did not differ either between experimental and control groups or between graft types. Our results support the conclusion that osteochondral allografts can be stored for as many as 14 days without significantly affecting the results of the procedure.

Animals↗
PubMed1995

In vivo effect of pressurization of polymethyl methacrylate bone-cement. Biomechanical and histologic analysis.

Sixteen goats underwent total hip arthroplasty, half with pressurized and half with unpressurized bone-cement. The animals underwent hemiarthroplasty of the contralateral hip immediately prior to sacrifice 6 weeks later. Samples were tested for interface strength and evaluated histologically. Pressurization of polymethyl methylacrylate improves the strength of the bone-cement interface in vivo, as well as in vitro. There is a regional variation in the strength of the bone-cement interface both in vivo and in vitro. The regional variation in the in vivo model is at least in part due to a biologic effect. Membranes forming at the bone-cement interface are usually fibrous and incomplete, allowing direct cement-to-bone contact. Membranes appear to be involved in the remodeling of bone. Polymethyl methacrylate causes significant necrosis of the cortex, with ensuing resorption of the cortical bone. There is a small, statistically insignificant trend toward increased resorption and decreased bone formation with pressurized cement. The amount of necrosis appears to be similar with pressurized and nonpressurized cement. Bone remodels to fill defects in the cement mantle.

Animals↗
PubMed1991

Fresh osteochondral allografting of the femoral condyle.

Fresh osteochondral shell allografting is conceived as an interim response to the localized loss of articular cartilage in young patients for whom there is no reasonable alternative after conservative procedures have failed. The concept is not new and has been investigated extensively in in vivo animal investigations. The functional and anatomic results of these studies, however, have been consistently unsatisfactory because of technical deficiencies and supposed immunogenic responses. The results of early clinical studies were variable, and despite more recent clinical work, the procedure has been considered at least investigational by some. The purpose of this study is to retrospectively review a series of patients treated with osteochondral allografting of the femoral condyle with particular emphasis on those done more than five years ago. No tissue-typing blood-group matching or gender distinction was made and immunosuppressant agents were not used. Size matching of the donor and recipient were essential to provide an orthotopic graft. Twelve knees were operated on more than five years ago. Of these twelve, three are not available for review. Nine knees have been observed for an average of 66 months and eight are rated good or excellent by a standardized rating scale. One knee rated poor seems to be the result of a technical deficiency. Since 1983, 37 fresh osteochondral allografts of the femoral condyle have been performed in 36 patients. Twenty-five of these have been performed in the last five years and the results to date are summarized.

Adolescent↗
PubMed1990

The calcar femorale. An anatomic, radiologic, and surgical correlative study.

In order to define the anatomy of the calcar femorale, a radiologic and surgical study was done on ten paired cadaver femurs. After radiography and computed tomographic (CT) scans, the specimens were subjected to medullary reaming by an experienced orthopedist, simulating total hip arthroplasty procedures. The imaging studies were repeated and compared with the prereaming studies. The calcar femorale was dissected from surrounding medullary bone, and sections of this structure were examined histologically. The calcar femorale is a condensation of cancellous bone. It is not affected by the reaming procedure but may play a role in guiding the reamer. This structure is separate from the calcar area described in relation to bone resorption after hip arthroplasty.

Cadaver↗
PubMed1990

Acetabular augmentation in primary and revision total hip arthroplasty with cementless prostheses.

Twenty-four consecutive cementless hip arthroplasties (13 autografts and 11 allografts) have been done in which large bone grafts were used to augment major acetabular deficiencies and have been followed for a minimum of 24 months with a mean of 34 and a maximum follow-up period of 55 months. The autograft augmentations were uniformly successful. Two fixation failures occurred in the allograft group. Considering the extreme deficiency in the acetabulae encountered and the absence of sufficient autograft material in this group of patients, the use of frozen allografts (although less successful in this series) seems justified. Graft resorption as determined by direct roentgenographic measurements was less than might be expected but may be a manifestation of the short-term follow-up period. Resorption, however, was greater in the allograft group and, when marked, was associated with fixation failure.

Acetabulum↗
PubMed1989

Intramedullary plugs in cemented hip arthroplasty.

The use of intramedullary plugs in cemented total joint arthroplasty is currently considered standard practice by most surgeons. In this in vitro study, the authors evaluated the holding power, migration, and leakage of four commonly used plug types--bone, acrylic bone cement, and two polymeric plugs from different manufacturers. Only acrylic bone cement plugs prevented distal leakage of cement and did not migrate under the influences of pressurized cement injection.

Bone Nails↗
PubMed1989

Resurfacing of the knee with fresh osteochondral allograft.

Fifty-nine fresh osteochondral allografts were consecutively transplanted into the knees of fifty-eight patients. The preoperative diagnoses were chondromalacia or degenerative arthritis of the patella, osteochondritis dissecans, a traumatic defect or osteonecrosis of the femoral condyle, a painful healed depressed fracture or traumatic defect of the tibial plateau, and unicompartmental traumatic arthritis of the knee. All of the patients had disabling pain after the failure of previous attempts to correct the problem surgically. Thirty-nine patients (forty knees) were available for follow-up at two to ten years after the allograft was transplanted. Nine transplants (22.5 per cent) failed and thirty-one (77.5 per cent) were successful. The result was rated excellent after thirteen of the successful transplants, good after fourteen, and fair after four. Transplantation of a fresh osteochondral allograft proved to be a satisfactory intermediate procedure for the treatment of the disabling conditions, except unicompartmental traumatic arthritis, in the young patients in this series. For the patients who had unicompartmental traumatic arthritis, the rate of success was only 30 per cent.

Adolescent↗
PubMed1988

Sustained pressurization of polymethylmethacrylate: a comparison of low- and moderate-viscosity bone cements.

There is at present great uncertainty relating to the fixation of joint implants. The deficiencies of acrylic bone cement are well documented, but the limitations of cementless fixation are as yet imcompletely identified. The purpose of this study was to investigate the potential of sustained external pressurization to improve the mechanical characteristics of conventional acrylic bone cement. The effect of serially increasing sustained pressurization of two commerically available acrylic bone cements (Simplex-P and LVC) was evaluated in human cadaver femora. A new method for determination of the shear strength of the bone-cement interface in place of the traditional pushout tests was used. In this model, there was a significant increase in the bone-cement interfacial shear strength with increasing pressure, but no difference in the shear strength was found between the two cements. At all pressure levels, the shear strength of the cement was greater than that previously reported. Increased cement penetration into the cortical bone was demonstrated with increasing pressure and low-viscosity cement, but the extent of cement penetration did not correlate with the shear strength of the bone-cement interface.

Adult↗
PubMed1987

Regional variation in shear strength of the bone-polymethylmethacrylate interface.

Many investigators consider the polymethylmethacrylate-bone interface the weakest link in the bone-cement-implant system. Push-out tests, frequently used for in vitro evaluation of the bone-cement interface, produced inconsistent results of shear strength. Therefore, a more reliable model for testing the shear failure of the interface was developed. Better understanding of intrinsic variations in bone quality and geometry of endosteal bone at the interface may yield important insight into the patterns of clinical failure of cemented total joint prostheses.

Biomechanical Phenomena↗
PubMed1986

Intraoperative osteoscintigraphy as an aid to bone biopsy.

A new use for intraoperative bone imaging is described. The technique allowed accurate localization of bone pathology for biopsy where plain radiographs and bone morphology were otherwise normal. The technique should increase diagnostic accuracy and eliminate false-negative biopsy results.

Adenocarcinoma↗
PubMed1986

Cement composite delivery system.

Several new and innovative techniques have recently been introduced that purport to increase the strength of polymethyl methacrylate bone cement. One of these concepts is the use of carbon and polymer fibers to form a cement composite. Bone cement composites usually 1% fiber, are very difficult to use clinically. The composite is very sticky and viscous, which precludes effective hand packing or the use of conventional delivery systems. A new delivery system for very viscous materials is presented and examples of in vitro application are shown.

Animals↗
PubMed1982

The erythrocyte sedimentation rate in orthopaedic patients.

The ESR, a sensitive measure of the inflammatory response, is elevated in 90% of patients who have serious orthopedic infections, e.g., discitis, septic arthritis, and hematogenous osteomyelitis. In most cases, it is sufficient to distinguish these entities from the less serious disease states, i.e., transient synovitis. After major surgical operations or extensive trauma, the ESR often increases to high levels and, if sepsis does not supervene, it returns to normal within six months. Outpatient determination of the ESR, although useless in the early detection of malignancy, is valuable in detecting inflammatory arthridities and major sepsis.

Arthritis, Infectious↗
PubMed1980

The spherocentric knee: a re-evaluation and modification.

The purpose of this study was to assess prospectively the initial results of total knee replacement with the standard spherocentric component and to identify retrospectively the pathogenesis of any unsatisfactory results. As a consequence of this study, the femoral component was modified. Thirty-six knees were reviewed twenty-two to fifty-two months after a standard spherocentric total knee replacement, with a mean follow-up of thirty-five months. Twenty-five (70 per cent) of the knees had significant relief of pain and improved function. Eleven knees were not improved because of confirmed loosening in five, supracondylar fracture in two, infection in one, and suspected loosening in three. Ten of these eleven complications became manifest within the first postoperative year. Alignment in the coronal plane was not consistently precise and hyperextension was a recurrent problem in twelve of the thirty-six knees. A modification in the femoral component was made: the stem was lengthened to 10.0 centimeters and the body was reoriented so that there was 5 degrees of valgus and 15 more degrees of posterior rotation than the original design. This modified prosthesis was used in twenty-five additional knees, with definite improvement in alignment, but the follow-up was insufficient to ascertain the effect of the modification on lossening and fracture.

Adult↗
PubMed1978

Fracture-dislocation of the dorsal-lumbar spine. Acute operative stabilization by Harrington instrumentation.

Twenty-four patients (of whom 17 were paraplegic) with acute fracture dislocations of the dorsal-lumbar spine underwent stabilization with Harrington instrumentation and were followed for an average of 16 months. Immediate postoperative ambulation was achieved in 16 patients. There was little difference between compression and distraction with respect to reduction and maintenance of correction. Compression rods resulted in solid union in 15 of 16 patients, while distraction rods were successful in 6 of 8 instances. In contrast to reported series in which operative intervention has been avoided, at least a 50% reduction in total hospitalization stay and costs has been achieved. Functional results were comparable to or exceeded the results of other series, and complication rates were similar with the exception of postoperative pain in 2 patients.

Adolescent↗
PubMed1977

Polyarticular disability: a functional assessment.

The purpose of this study was to design and evaluate a system for the functional evaluation of patients with polyarticular disease. A single assessment can be done in approximately 15 minutes. Extensive prior preparation is not required. The evaluation is reproducible and the numerical characterization agrees well with a physician's overall assessment of functional impairment. The subscores can be used independently of the total score to focus on specific areas of disability. Use of the evaluation in other institutions has produced a high degree of reliability. Statistical evaluation has demonstrated areas of weakness that have been eliminated or modified to increase reliability of the system.

Activities of Daily Living↗
PubMed1975

The relative safety of polymethylmethacrylate. A controlled clinical study of randomly selected patients treated with Charnley and ring total hip replacements.

Forty patients from a group of seventy elected to participate in a prospective randomized clinical study designed to evaluate the systemic effects of polymethylmethacrylate implanted with a Charnley total hip replacement, utilizing patients treated with a Ring total hip prosthesis ad controls. Intraoperative alterations in cardiovascular function were related to use of methylmethacrylate, but postoperative changes in pulmonary function, erythrocyte sedimentation rate, serum lactic acid dehydrogenase, serum glutamicoxalacetic transaminase, and alkaline phosphatase were not. Charnley total hip replacements were associated with more ectopic-bone formation twelve months postoperatively. The two "latent" infections recognized during the thirty-four months of the study were in hips without acrylic fixation.

Alkaline Phosphatase↗