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Biomedical subjects

A G Binnington

Publications and source records attributed to A G Binnington.

At least 19 recordsLinked to original sources
PubMed2000

Cementless acetabular fixation in total hip arthroplasty using polyglycolide-lactide screws: an in vivo canine study.

Bone ingrowth into cementless acetabular components was evaluated in a canine total hip arthroplasty model, comparing components initially stabilized with polyglycolide-lactide screws with those initially stabilized with titanium screws. The acetabular shell was anchored with 2 polyglycolide-lactide screws in 16 dogs and with 2 titanium screws in 12 dogs. The dogs were followed and sacrificed at 7 weeks, 14 weeks, 10 months, or 15 months. Histomorphometric analysis of bone ingrowth into the weight-bearing dome of the acetabular shell was conducted. No difference was detected in mean bone ingrowth into the acetabular shell comparing the 2 screw groups. The results of this study do not support a significant advantage to the use of biodegradable screws for the initial stabilization of cementless acetabular components in canine total hip arthroplasty.

Acetabulum↗
PubMed1999

Use of a polyglycolide lactide cement plug restrictor in total hip arthroplasty.

The use of a polyglycolide lactide cement plug restrictor in cemented femoral fixation during total hip arthroplasty was evaluated. Femoral cement pressurization was evaluated in vitro in a cadaveric model and the host response to polymer degradation was evaluated in vivo in a canine total hip arthroplasty model. Sixteen embalmed anatomic specimen femurs were prepared for cement femoral fixation. The intramedullary canal was plugged with either an ultrahigh molecular weight polyethylene cement plug restrictor or a polyglycolide lactide cement plug restrictor. Peak pressures in the proximal, mid, and distal portions of the cement mantle were recorded during cement insertion, cement pressurization, and implant insertion. There was no difference between the two plug groups in peak pressures throughout the cement mantle during cement insertion, pressurization, or implant insertion. Total hip arthroplasty using a cementless acetabular component and a cemented femoral stem was performed in 24 dogs. The femoral intramedullary canal was plugged with a polyethylene or a biodegradable cement plug restrictor. The dogs were sacrificed at 7 weeks, 10 months, or 15 months. Radiographically, no osteolytic lesions were seen around either plug type. Histomorphometrically, the polyglycolide lactide plugs appeared intact at 7 weeks and partially degraded by 10 and 15 months. In both plug groups, a mild fibrohistiocytic reaction with infiltration of fibrocytes, histocytes, and endothelial cells was seen. No osteolysis was observed. The results of the current study show that femoral cement pressurization can be attained in vitro using a biodegradable cement plug restrictor and that for as long as 15 months in the in vivo canine model there were no adverse reactions associated with use of these plugs compared with conventional ultrahigh molecular weight polyethylene plugs.

Animals↗
PubMed1995

The effect of the medial collar in total hip arthroplasty with porous-coated components inserted without cement. An in vivo canine study.

We performed an in vivo study in a canine model to compare the results of the use of a porous-coated collared femoral component with those of the use of a porous-coated collarless femoral component in total hip arthroplasties without cement. Our study focused on the comparative proximal strain pattern, bone ingrowth, and cortical porosity of the two types of prostheses. We used a trochanteric wire marker to measure subsidence. The use of the limb was assessed with gait analysis. Twelve weeks after the operation, the collarless components had significantly greater bone ingrowth proximally (p = 0.003) and were associated with significantly lower cortical porosity (p = 0.006). There were no differences between the groups with regard to either axial or hoop strain. While the group that had a collarless prosthesis had significantly less proximal-medial radiolucency (p = 0.03), there were no differences between the groups with regard to subsidence.

Animals↗
PubMed1994

Fixation with biodegradable devices of acetabular components in a canine model.

Cementless total hip arthroplasty was performed in 13 dogs. The acetabular component was anchored with two biodegradable devices (polylactic acid) in seven dogs and with two titanium screws in six dogs. At 14 weeks, histomorphometric determinations of bony ingrowth into the porous coating of the acetabular weight bearing dome was 54.4% when fixed with the biodegradable devices and 58.9% when fixed with the titanium screws (no statistically significant difference; p = 0.556). At the sites of fixation, less bony ingrowth occurred with the biodegradable devices. The use of biodegradable devices in total hip arthroplasty should overcome the potential metal corrosion of titanium screws that can lead to polyethylene wear.

Animals↗
PubMed1992

The intestinoprostatic capsule anastomosis: functional and anatomic results in a canine model.

Because of its potential application to intestinal bladder reconstructions, the authors studied the functional and anatomic results of a modification of the Camey procedure. In this modification the enteric bladder replacement is sutured to the periphery of the prostatic capsule after the inner two-thirds of the prostate gland have been removed. In eight dogs postoperative functional studies revealed that all were continent and potent. Autopsy examination of the area of the intestinoprostatic anastomosis revealed that the prostatic fossa was lined by a transitional epithelial layer originating from the urethral stump and not by intestinal mucosa as might be expected. The results indicated that this modification is simpler technically than the original procedure, that it shortens the operating time and that it gives excellent functional results. If used in the context of bladder cancer, however, the procedure should be undertaken only in the presence of negative biopsies and brushings of the urethra before surgery, because the transitional epithelium lining the prostatic fossa represents a new area at risk later malignant transformation. Moreover, because of the potential importance of the area of prostatic fossa resurfaced postoperatively by urothelium, even patients with normal preoperative urethral biopsies and brushings who undergo such a procedure require careful follow-up with endoscopic examination, urethral biopsy and brushings and cytologic examination of the urine.

Anastomosis, Surgical↗
PubMed1987

The effect of proximally and fully porous-coated canine hip stem design on bone modeling.

Porous coated canine femoral hip replacement implants were evaluated for biological fixation by bone ingrowth and the effect of the extent of porous coating on bone modeling. The Co-Cr alloy implants were either fully porous coated or coated only on the proximal 40% of the stem. Two implants of each type were studied 9, 16, and 36 months after surgery. Implant fixation and bone modeling were assessed radiographically throughout the implant periods and histologically after the test animals were killed. All 12 implants appeared stably fixed within the femur and were bone-ingrown in the porous region. Radiographic features such as proximal medial and anterior cortical thinning, proximal cancellous bone hypertrophy, and new endosteal bone formation near the stem tip were noted within the first postoperative year, with no appreciable change thereafter. The extent of proximal cortical thinning varied from virtually none to as much as 40%, being more prominent with the proximally coated implants at 16 months and with the fully coated implants at 36 months. Of consistent note was cancellous hypertrophy at the junction of porous and smooth implant surfaces with proximally coated implants and new endosteal bone formation and ingrowth at the stem tip of fully coated implants. These results indicate that the proximally porous-coated implant design causes increased proximal stress transfer, but this does not necessarily preclude proximal cortical resorption.

Adaptation, Physiological↗
PubMed1982

The effect of neurogenic stimulation on the development and growth of bony tissues.

In order to elucidate the mechanisms of neurogenic control of bone development and growth, the effects of traumatic and electric stimulation on the development, size, and shape of antler bone tissue were investigated. Unilateral growth of antler in a female deer was initiated after traumatic stimulation of the frontal bone. Electrical stimulation of antler nerves or antler periosteum resulted in an increase in more than 70% in antler length and over 40% in weight. Stimulation of antler nerves also resulted in abnormal shape of antlers. The role of periosteal nerves and the participation of the central nervous system in the responses to stimulation is discussed.

Aging↗
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↗
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↗
PubMedDate not supplied

Enterocystoplasty with cystectomy and subtotal intracapsular prostatectomy in the male dog.

Urinary diversion by implantation of the ureters into an isolated segment of jejunum was evaluated in eight clinically normal male dogs. Total cystectomy and subtotal intracapsular prostatectomy were performed, and the intestinal loop was sutured to the prostatic remnant. General health, renal function, acid-base balance, urinary tract infection, and urinary continence were monitored during observation periods of 4 to 30 weeks. All dogs survived the observation period and seven were in excellent general health at the time of euthanasia. Six of the 16 ureterointestinal anastomoses were complicated by complete ureteral obstruction. Absorption of urea from the intestinal loop was speculated as the reason for significant increases in serum urea nitrogen concentrations in all of the dogs. Serum creatinine concentrations generally remained within the normal range, but were significantly increased from preoperative baseline values by week 30. There was dilation of 12 renal pelves and ureters in seven dogs. Urine bacterial cultures were positive in six dogs, but histologic evidence of pyelonephritis was present in only five kidneys. Ejaculation was not affected by the procedure, but epididymitis was present in five dogs. The dogs could urinate consciously and did not dribble urine continuously; however, they urinated hourly. While the procedure was well tolerated by the dogs, the frequency of urination makes this technique unacceptable for most household pets.

Anastomosis, Surgical↗
PubMedDate not supplied

Renal allograft survival in outbred mongrel dogs using rabbit anti-dog thymocyte serum in combination with immunosuppressive drug therapy with or without donor bone marrow.

Therapeutic renal transplantation in dogs is currently being investigated as a treatment for endstage renal disease. This pilot study examines the effect of donor bone marrow (DBM) infusion and antithymocyte serum (ATS) in combination with immunosuppressive drug therapy in prolonging renal allograft survival in dogs. Seven normal outbred mongrel dogs received an unmatched renal allograft. All dogs received rabbit anti-dog thymocyte serum (RADTS), prednisone (Pr), cyclosporine-A (CsA) and azathioprine (Aza). In addition, three dogs (group 1 test) received DBM and four dogs (group 2 control) did not receive DBM. Serum CsA levels were measured throughout the study. Immunosuppressive therapy was gradually reduced with Pr, CsA, and Aza withdrawn at 200, 450, and 680 days, respectively. Allograft rejection was treated with prednisolone sodium succinate. One dog in group 1 and one in group 2 died as a result of infectious canine rhinotracheitis and rejection early in the study. Renal allograft torsion occurred in one group 1 dog. The remaining four dogs survived the 2 years of the study. The dogs in group 2 (three dogs) all rejected the renal allograft after total drug withdrawal, the surviving dog in group 1 did not. This study demonstrates that RADTS, Pr, CsA, and Aza in combination can prolong renal allograft survival in mongrel dogs, whereas DBM may enhance the unresponsive state.

Animals↗
PubMedDate not supplied

The effect of occlusive and semi-occlusive dressings on the healing of acute full-thickness skin wounds on the forelimbs of dogs.

This project compared the effects of hydrocolloid (HC) and hydrogel (HG) occlusive dressings and a polyethylene (PE) semi-occlusive dressing on the healing of acute full-thickness skin wounds on the forelimbs of 10 dogs. All treatments resulted in a similar degree of healing at postoperative days 4 and 7. No significant differences existed in the number of wounds that were more than 90% healed at postoperative day 28 between the group treated with the HG dressing and the group treated with the PE dressing. There were significantly fewer wounds more than 90% healed at postoperative day 28 in the group treated with the HC dressing. Wounds under the HG dressing had the largest mean percentage of contraction at postoperative days 21 and 28. Wounds under the HG dressing also had the largest contraction/re-epithelialization ratio (postoperative days 21 and 28) compared with wounds under the PE and HC dressings. Wounds under the PE dressing had a significantly higher mean percentage of re-epithelialization than wounds under both occlusive dressings on postoperative days 14, 21, and 28. Wounds under the two occlusive dressings had exuberant granulation tissue present more often than wounds under the PE dressing. The two occlusive dressings had significantly higher bacterial counts on wounds compared with wounds under the PE dressing; analysis of variance (ANOVA), P = .0008. Wounds under the HC dressing showed the poorest healing in all parameters.

Animals↗
PubMedDate not supplied

Half-body radiotherapy. Evaluation of the technique in normal dogs.

Eight healthy mongrel dogs were treated with half-body irradiation (HBI) in a pilot study to evaluate the technique and radiotolerance of different organs. Cranial and caudal half-body fields were established using the 13th thoracic vertebra as the dividing point. Under general anesthesia, either 7 or 8 Gray (Gy) were delivered to one half of the body using opposing radiation portals. The other half of the body was similarly treated 28 days later. The dogs were monitored for 12 months. Significant radiation effects included transient bone marrow suppression and radiation sickness. There were no serious or life-threatening problems, but the 8 Gy group consistently showed more severe clinical signs and histologic changes than the 7 Gy group. Total body irradiation in two fractions of 7 or 8 Gy given 1 month apart appears to be a safe treatment that can be developed for therapy in veterinary oncology.

Animals↗
PubMedDate not supplied

Half-body radiotherapy in the treatment of canine lymphoma.

In a Phase I-II study, half-body radiotherapy was used to treat 14 dogs with multicentric lymphoma. Using this technique, a radiation dose of 7 Gray (Gy) was delivered to one half of the body in a single exposure. The other half of the body was treated approximately 28 days later. Of 14 treated dogs, 11 (79%) had a measurable decrease in tumor size. Five dogs achieved a complete or partial remission with a mean duration of 102 and 54 days, respectively. In predicting response to therapy, poor prognostic factors included large tumor burdens, advanced disease stage, and chemotherapy-resistant tumors. Side effects of treatment were divided chronologically into acute (radiation sickness, tumor lysis), subacute (bone marrow suppression), and chronic (radiation pneumonitis, lymphoma-cell leukemia) syndromes. Complications were more severe in tumor-bearing dogs when compared with healthy control animals. Dogs with small tumor burdens and minimal internal disease had fewer complications compared with those with more advanced disease.

Animals↗
PubMedDate not supplied

The composite Corethane/Dacron vascular prosthesis. Canine in vivo evaluation of 4 mm diameter grafts with 1 year follow-up.

Polyurethane vascular prostheses offer the potential of superior thromboresistance and reduced anastomotic hyperplasia compared to existing Dacron and ePTFE alternatives, but have suffered from susceptibility to biodegradation, with resulting mechanical failure. To address this problem, the authors have developed and evaluated a composite prosthesis comprised of: 1) an inner blood interfacing elastomeric porous membrane made from Corethane, a proprietary Shore 80A polyurethane like material substantially devoid of ether/ester linkages, with superior biostability over conventional polyether urethanes, spun into a nonwoven structure with fiber diameters 10-15 microns and pore sizes 30-60 microns filled with gelatin +/- heparin; and 2) an outer soft, tissue interfacing, warp knitted Dacron mesh bonded to the inner layer to assure long-term dimensional stability. Twenty 4 mm ID x 5 cm L composite prostheses, half with heparinized gelatin (the remainder nonheparinized) were implanted as femoral interposition grafts in 10 dogs. Four of the 10 nonheparinized grafts occluded. All 10 with heparin remained widely patent, with two explanted at 6 months showing vascularized connective tissue growth through the graft, in contrast to the giant cell inflammatory response to the Dacron mesh, with a substantially endothelialized neointima and no Corethane biodegradation. Of the 10 patent grafts at 1 year follow-up, none showed aneurysm formation. This vascular prosthesis provides compliance superior to ePTFE and Dacron alternatives, with excellent suture retention and good kink resistance, while combining the superior thromboresistance and tissue ingrowth properties of polyurethanes with the proven biostability of Dacron.

Animals↗