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Biomedical subjects

G J Rogers

Publications and source records attributed to G J Rogers.

11 recordsLinked to original sources
PubMed1999

Nitrous acid pretreatment of tendon xenografts cross-linked with glutaraldehyde and sterilized with gamma irradiation.

Collagenous xenografts made from kangaroo tail tendon cross-linked with glutaraldehyde have a potential application in the reconstruction of massive digital tendon deficits. However, a limitation to the clinical use of these xenografts has been the optimization of collagen cross-linking, and subsequent bio-incorporation and retention of mechanical properties following implantation. The purpose of this study was to evaluate the effect of nitrous acid on modulating the biologic and mechanical properties of tendon xenografts cross-linked with glutaraldehyde. Tendon xenografts were pretreated with 0.1 or 0.01 M nitrous acid solution, prior to cross-linking in 2% glutaraldehyde and sterilization by gamma irradiation. Xenografts were implanted intramuscularly in rabbits to examine biocompatability, and also used to repair ovine digital extensor tendon deficits to evaluate functional incorporation. Histologically, intramuscularly implanted nitrous acid pretreated xenografts in rabbits had a greater degree of diffuse cellular infiltration into interstitial splits in the graft than controls after 12 weeks. Xenografts implanted in an ovine extensor tendon deficit were evaluated after 26 and 52 weeks. Rate of failure of tenorrhaphies between host tendon and xenografts overall (15/21) was significantly greater (P < 0.05) than for autografts (1/21), suggesting that the holding power of sutures in xenografts was inferior to that obtained in autografts. Tensile failure stress of midsections of both nitrous acid pretreated and control xenografts was about 100 MPa prior to implantation (time zero). After 26 and 52 weeks, failure stress of both types of xenografts was significantly less than at time zero (P < 0.05). At 52 weeks, failure stress of nitrous acid pretreated xenografts (47.4 +/- 3.1 MPa) was significantly less than control xenografts (63.7 +/- 5.4 MPa); (P < 0.05). However, nitrous acid pretreated xenografts were similar to control xenografts in failure load (357 +/- 29 and 354 +/- 26 N, respectively), but they tended to have larger cross-sectional areas (7.6 +/- 0.5 versus 5.7 +/- 0.6 mm2, respectively) which were responsible for the lower calculated value for failure stress. Histologically, autografts maintained their normal tissue architecture and evoked a more limited cellular response in surrounding tissues than xenografts (P < 0.05). Both types of xenograft were surrounded by a thicker cuff of cellular response than autografts. However, compared to control xenografts, nitrous acid pretreated xenografts had more extensive fragmentation and splitting of collagen bundles, and more diffuse cellular and vascular infiltration into these interstitial splits, and these alterations were apparently contributing to the greater 'swelling' of these xenografts. It was concluded that pretreatment of tendon xenografts with nitrous acid modulated their biologic and material properties. Further studies are needed to elucidate the mechanism of these effects, and to determine if the protocol for tendon xenograft preparation could be optimized for improved clinical performance.

Animals↗
PubMed1995

Shielding of augmented tendon--tendon repair.

Strength and function of autogenic and xenogenic reconstruction of digital extensor tendons was examined in an ovine model. In this study, tendon-graft junctions were formed by either suture augmented with a woven polyester tube (A), or augmented and shielded from surrounding tissues by chemically-treated bovine pericardium (S). By 12 wk, both A and S sheep had returned to full range of motion. Mechanical strength of both the autograft-host and xenograft-host repair sites was similar, with a pooled strength of 131 +/- 25 N (n = 15). Similarly, the mid-portion xenograft strengths were constant at approximately 366 +/- 97 N (n = 7). In contrast, mid-portion autograft strengths decreased from 380 +/- 110 N (N = 4) to 120 +/- 66 N (n = 4) if shielding was omitted. The loss in autograft strength was attributed to loss of function associated with adhesions. The use of the augmentation device coupled with an adhesion barrier gives higher initial reconstruction strength and improved function during the host repair period up to 12 wk.

Animals↗
PubMed1992

The effect of gamma irradiation on a xenograft tendon bioprosthesis.

Radiation sterilisation of xenograft prostheses has been shown to cause damage to the material. Such damage has been imputed to affect the mechanical and biological properties and may contribute to long-term failure. This study has examined the effect of 25 kGy (2.5 Mrad) of gamma radiation on the mechanical and physicochemical properties and the biological function of a xenograft tendon bioprosthesis derived from glutaraldehyde cross-linked kangaroo tail tendon. The ultimate tensile stress of nonirradiated glutaraldehyde cross-linked tendon was greater than that of fresh frozen tendon, but irradiated cross-linked tendon did not differ. Irradiation did not alter the response to prolonged collagenase exposure. There was a decrease in overall apparent cross-link density (as determined by thermal denaturation temperature). After 12 months implantation, there was a slightly more active cellular response around irradiated tendon and the very peripheral fibres were infiltrated, but the mechanical properties of the retrieved implants were the same for irradiated and nonirradiated material. Gamma irradiation would appear to be a satisfactory method of sterilisation for glutaraldehyde cross-linked tendon materials. However, as damage to the cross-linked structure was detected in this study, it may not be appropriate in other applications.

Animals↗
PubMed1991

Treated xenografts as gliding tendon prostheses in an ovine model.

A model for testing the properties of gliding tendon grafts has been developed that allows anastomoses to be evaluated separately from the mid-portion of the graft. In addition, two different graft materials may be implanted in one sheep foreleg whilst maintaining control (not operated) tendons in both the operated leg and contralateral foreleg. The model has been used to evaluate the response of xenografts made from chemically treated kangaroo tail tendon (KTT) compared with autografts. At 3 month the mid-sections of the glutaraldehyde-fixed xenografts maintained between 57 and 82% of their initial ultimate tensile strength whereas lyophilized KTT dropped to 10% and autografts retained 91% of initial strength. Sterilization by gamma-radiation of wet xenografts did not affect the material and implant properties significantly. Longer term studies are necessary to determine the resorption behaviour of the xenografts. Anastomosis strengths were found to be about the same for all grafts, at about 25% of the strength of the original tendon. Alternatives need to be investigated to improve this strength.

Anastomosis, Surgical↗
PubMed1991

Autograft and Leeds-Keio reconstructions of the ovine anterior cruciate ligament.

This study compared the Leeds-Keio prosthesis with grafting of autogeneic patellar tendon for the reconstruction of the ovine anterior cruciate ligament under controlled conditions. Reconstructed knees from six sheep of each group were evaluated at 12, 26, and 52 weeks postreconstruction with respect to clinical assessment, gross pathology, mechanical properties, and histology. Although no difference in clinical assessment (anteroposterior draw, range of motion, and function) was noted between the prosthesis reconstruction and the autograft reconstruction, the prosthesis provided a higher strength initially, which remained relatively constant over the one-year study. However, prosthesis wear was observed, with up to 50% of Dacron fibers ruptured in some cases. Histologic sections indicated that in the ovine model, the Leeds-Keio prosthesis should be considered an artificial device and not a scaffold or stent that supports aligned collagenous growth. The autograft had low strength at 12 weeks, which increased over the study period. Despite acceptable clinical performance and adequate mechanical properties up to one year postimplantation, neither reconstruction approached the clinical or mechanical performance of the normal anterior cruciate ligament in the ovine model.

Animals↗
PubMed1990

Measurement of the mechanical properties of the ovine anterior cruciate ligament bone-ligament-bone complex: a basis for prosthetic evaluation.

The reported ultimate tensile stress of the anterior cruciate ligament varies greatly, ranging from 13 to 147 MPa. This study shows that the orientation and degree of flexion of the bone-ligament-bone complex significantly alter the apparent ultimate tensile properties (ultimate tensile stress ranging from 60 +/- 3 to 123 +/- 15 MPa, ultimate specific extension from 37 +/- 7 to 93 +/- 20%), whilst the method chosen for measuring extension also affects the calculated specific extension of the bone-ligament-bone complex. It is suggested that, for considerations of prosthesis design and evaluation, the mechanical properties of the bone-ligament-bone complex should be measured in anterior draw and extension measured using points as close as possible to the positions of the ligamentous attachment sites.

Animals↗
PubMed1989

Recurrent stenosis by duplex scan following carotid endarterectomy.

Between June 1984 and January 1986, 155 carotid endarterectomies were performed with routine shunting. Serial duplex scanning was performed during an 18-month period on 124 vessels. The results of this duplex scan review revealed the following data: A normal scan was obtained in 87/124 (70.1%). Recurrent stenosis was identified in 35/124 (28.1%), and an occluded vessel was identified in 2/124 (1.6%). Of the total recurrent stenosis group, recurrent stenosis was graded mild in 22/124 (17.7%), moderate in 7/124 (5.6%), and severe in 6/124 (4.8%). Of the 35 vessels with recurrent stenosis by duplex scanning, 22/35 (62.8%) were in female patients, and 13/35 (37.2%) were in male patients. Of the vessels with severe recurrent stenosis, 5/6 (83%) were in female patients. Recurrent stenosis following carotid endarterectomy is more common than appreciated clinically, and female patients in particular may be more prone to recurrent stenosis.

Adult↗
PubMedDate not supplied

Anterior cruciate ligament graft fixation. Initial comparison of patellar tendon and semitendinosus autografts in young fresh cadavers.

The initial biomechanical properties of semitendinosus and patellar tendon autografts and their fixation strengths were investigated. Twenty fresh cadaveric knees from donors under 42 years of age were used in the study. After removing all soft tissues other than the anterior cruciate ligament, we determined the ultimate tensile strength (2195 +/- 427 N) and stiffness (306 +/- 80 N/mm) of the anterior cruciate ligament in nine knees. In six knees, anterior cruciate ligaments were reconstructed using an autologous patellar tendon graft with proximal and distal interference fit screws; this resulted in an ultimate tensile strength of 416 +/- 66 N. Five knees were reconstructed with quadruple-stranded (double-looped) semitendinosus tendons fixed proximally by a titanium button and braided tape and distally by tibial post screw. This resulted in an ultimate tensile strength of 612 +/- 73 N, which was significantly higher than the strength in the patellar tendon group. Graft stiffness did not differ between the groups and was 47 +/- 19 N/mm (N = 11). This study demonstrates that the reconstructed knees had only 20% to 30% of the ultimate tensile strength of the normal anterior cruciate ligament. In summary, the semitendinosus reconstruction using a button for proximal fixation is, at the time of surgery, approximately 50% stronger than patellar tendon reconstructions with similar stiffness.

Adult↗