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Biomedical subjects

J Dunlap

Publications and source records attributed to J Dunlap.

14 recordsLinked to original sources
PubMed1990

Effect of various methods of restoring flexor sheath integrity on the formation of adhesions after tendon injury.

The effect of three different methods of restoring flexor sheath integrity on the formation of adhesions around traumatized flexor tendons was studied by use of a chicken animal model. The three methods were: I, Primary sheath repair; II, a fascia patch; and III, a synthetic polytetrafluoroethylene surgical membrane patch. These were compared with controls in which the flexor sheath was excised. Adhesion formation was assessed both biomechanically by measuring the parameter work of flexion, (which represents the resistance to tendon gliding caused by adhesions), and also histologically. At 3 and 6 weeks there was no significant difference in the work of flexion between either the sheath repair or fascia patch digits, and the sheath excised controls. However, use of the synthetic polytetrafluorethylene patch did result in tendon gliding, which was significantly better than the controls. In contrast, at 12 weeks all three methods of sheath reconstruction had similar tendon gliding biomechanics, and all were significantly better than the controls. Histologically, at 3 weeks, the biologic barriers sheath repair and fascia patch were associated with a layer of granulation tissue, which adhered to the underlying tendon. This was similar to the appearance of the sheath excised control digits. The synthetic patch was not associated with a significant inflammatory reaction at this time period and was clearly separated from the tendon. However, by 6 and 12 weeks the granulation tissue in all three sheath reconstruction groups had undergone remodeling to a greater degree than had the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Biomechanical and histologic evaluations of pulley reconstructions in nonhuman primates.

A2 pulleys were reconstructed in nonhuman primates using expanded polytetrafluoroethylene, woven nylon, and fascia. Biomechanical and histologic evaluations were done after death at 18 weeks. Tendons were normal after all pulley reconstructions. Polytetrafluorethylene had a greater breaking strength than woven nylon or fascia, or control pulleys, both at 18 weeks and before implantation. Histologic analyses revealed fibrous ingrowth of host tissues, no adhesions, no trauma to underlying flexor tendons, and the absence of an inflammatory response, for all pulley types.

Animals↗
PubMed1989

Flexor tendon pulley reconstructions--a histological and ultrastructural study in non-human primates.

The feasibility of A2 pulley reconstructions using expanded polytetrafluoroethylene (PTFE), woven nylon, and fascia lata was assessed in a non-human primate model and evaluated by light and scanning electron microscopy 18 weeks after implantation. No adhesions were found between reconstructed pulleys and flexor tendons. All types of pulley were intact and incorporated by host tissues, without evidence of a foreign body reaction. The inner surfaces of the fascial and PTFE pulleys, apposed to the gliding flexor tendons, were smooth and covered by a fibrous layer of tissue on microscopic and ultrastructural examination. The apposed visceral synovial surfaces of the F.D.P. tendon were indistinguishable from those from unoperated digits. The FDP tenosynovium apposed to woven nylon pulleys was more fibrillar and granular. Based on the results of the present study and on previous biomechanical data, expanded PTFE should be considered as a material for pulley reconstruction; it is incorporated by host tissues, elicits no foreign body reaction and causes no adhesions or traumatic changes to underlying flexor tendons. It is not yet known whether it has sufficient breaking strength to meet the functional demands of human pulleys.

Animals↗
PubMed1989

Perfusion of the abductor digiti quinti after transfer on a neurovascular pedicle.

The perfusion to the abductor digiti quinti muscle was measured, both before and after, opponensplasty transfer on its neurovascular pedicle in six monkeys, with use of the hydrogen wash-out technique to determine blood flow. The musculotendinous unit can be transferred without vascular compromise, but detachment of the abductor digiti quinti from its origin on the pisiform results in ischemia. Such impairment of blood flow to the muscle may be responsible for the postoperative fibrosis, which has been seen as a complication of the procedure.

Animals↗
PubMed1989

Effect of fatty acid composition on insulin and IGF-I binding in retinoblastoma cells.

Receptors for insulin and other hormones are often influenced by their environment, including fatty acid content and membrane fluidity. Y79 retinoblastoma cells enriched with arachidonic or docosahexaenoic acid show an increase in membrane fluidity determined by fluorescence polarization using the plasma membrane-specific probe, trimethylammonium-diphenylhexatriene. Unlike cells enriched with polyunsaturated fatty acids, cells cultured in media containing palmitic or oleic acid showed no changes in membrane fluidity or fatty acid composition. Cells enriched with docosahexaenoic acid show an increase in insulin binding at 15 degrees C that is due to an increase in the number of available insulin receptor sites on the plasma membrane. In contrast, insulin binding is not altered in cells enriched with arachidonic, palmitic or oleic acid. Furthermore, the binding of insulin-like growth factor-I (IGF-I) in Y79 cells is not changed by the fatty acid unsaturation of the cell membrane. Because docosahexaenoic acid is naturally present in high concentrations in the retina these studies suggest it may have a role in modulating insulin binding and function.

Eye Neoplasms↗
PubMed1988

Sensitivity and specificity of somatosensory and neurogenic-motor evoked potentials in animals and humans.

The purpose of this study was to report the effects of spinal cord compression, ischemia, and distraction on clinical status, and somatosensory (SEP) and neurogenic-motor evoked potentials (NMEPs) in animals. The authors also reported their clinical experience with NMEPs elicited from humans undergoing surgery for spinal deformities. Results from the animal studies indicate that NMEPs are more sensitive and specific to the effects from spinal cord compression, ischemia, and distraction than SEPs. In every situation, NMEPs always correlated with the animal's post-surgical clinical status, while SEPs demonstrated an unacceptable false positive and false negative rate. In the 111 clinical cases in which NMEPs were administered, reliable NMEPs were easily elicited in more than 90% of the cases. In the remaining cases, no reliable NMEPs could be recorded because of procedural errors, which have been resolved. The results from this study suggest that the use of NMEPs should be considered as an adjunct to SEPs when monitoring spinal cord function during surgery.

Animals↗
PubMed1988

Osteoporotic correlates of alcoholism in young males.

A group of 22 white males (ages, 28 to 40 years) with histories of chronic alcohol abuse ranging from 1 to 21 years were evaluated for trabecular bone mineral density in the left femoral neck area. A group of age and weight-matched white males with no history of alcoholism served as controls. All participants completed medical history questionnaires regarding fracture history, dietary habits, medications, and physical activity. Singh femoral trabecular indices also were measured for the alcoholic participants. Analysis of bone mineral data as measured by dual photon absorptiometry revealed no statistically significant reduction in the bone mineral densities of the alcoholic group when compared to the controls. No differences were seen in the areas of the femoral neck, Ward's triangle, and greater trochanter. Duration of alcoholism also was not correlated with the degree of osteopenia. Singh index measurements of right and left femoral heads were compared and revealed no significant differences within individual patients. Left femoral Singh index values averaged 5.5 (range, 4 to 6) for the alcoholic group and were not indicative of decreased bone mineral density. It is concluded from this study that chronic alcoholism associated with heavy smoking most likely has a debilitating effect on the trabecular bone density of white males, yet clinical and radiographic evidence is not widely manifested in men under the age of 40 years.

Adult↗
PubMed1988

The effect of vascularization on avian flexor tendon repair. A biochemical study.

Although it has been demonstrated in experimental animals that vascular perfusion functions less effectively than diffusion as a nutrient pathway to the uninjured flexor tendon, it is recognized that the nutritional requirements of an injured flexor tendon may be different. The present study examines several biochemical parameters of avian flexor tendon repair, during a six-week period, in the presence of an intact vinculum longum and with the vinculum longum ligated. Formation of collagen/noncollagen protein, glycosaminoglycan synthesis, and tissue levels of both DNA and hexosamine were quantified. The absence of the vincular blood supply did not affect the levels of total DNA and hexosamine, did not alter the pattern of either protein or glycosaminoglycan formation in the early healing phase, and did not impair the overall synthesis of collagen and noncollagen protein throughout the six-week study period. However, the pattern of collagen and noncollagen protein synthesis differed in lacerated tendons during the period of repair; noncollagen protein synthesis peaked at ten days, while collagen synthesis increased uniformly throughout the 42-day period of study. There was a notable decrease in total matrix hydroxyproline (collagen) during repair, which continued throughout the entire first three weeks after laceration. Thus, the actual percentage of collagen synthesis decreased during the first three weeks of repair and began to return to its normal uninjured level by the sixth week.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Pathomechanics of posterior sag of the tibia in posterior cruciate deficient knees. An experimental study.

This study was an investigation of the pathomechanics of posterior sag of the tibia in knees with posterior knee instability caused by PCL deficiency. By using fresh cadaver knees, the authors hoped to define the relationship of the posterior joint capsule and the medial and lateral collateral ligaments (MCL, LCL) with posterior knee instability in the PCL deficient knee. Thirty newtons of posterior stress were applied to the knees to simulate postoperative conditions. Roentgenographic methods were then used to evaluate posterior sag and change in the distance between the origin and insertion of the PCL. Strain gauges were used to measure the actual strain of the PCL and the collateral ligaments. The PCL, the posterior capsule, and the medial and lateral collateral ligaments were sequentially divided and the above measurements were then repeated in the same way, using 30 N of applied posterior stress. When only the PCL was cut, posterior sag and medial rotation of the tibia occurred with increasing severity as flexion increased. No sagging or rotation of the tibia was observed at full extension in the knees that had isolated PCL "injury". When the posterior capsule was sectioned, no significant changes were noted in the severity of the sag or the rotation. When the MCL or LCL was divided in a PCL deficient knee, greater sag occurred with flexion and a significant sag was observed even at full extension. The MCL "injury" was associated with increased medial rotation, whereas LCL "injuries" were associated with lateral rotation of the tibia.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMedDate not supplied

Quantification of the perfusion of the anterior cruciate ligament and the effects of stress and injury to supporting structures.

The perfusion of the normal ACL was quantitated using the hydrogen washout technique in a canine model. This was compared to the perfusion of the synovium in the suprapatellar pouch. Changes in the ACL perfusion were quantitated after the application of anterior stress, division of the infrapatellar fat pad, and dissection of the synovium enveloping the ACL. The ACL is relatively hypovascular, with one-half the blood flow of the synovium of the suprapatellar pouch. Application of an anterior stress diminishes the blood flow to the ACL to one-fifth of the baseline value, an effect which is reversible. Division of the infrapatellar fat pad causes a two-fold decrease in perfusion to the ACL, whereas dissection of the enveloping synovium results in a complete cessation of blood flow.

Animals↗
PubMedDate not supplied

A nonparallel, nonisometric synthetic graft augmentation of a patellar tendon anterior cruciate ligament reconstruction. A model for assessment of stress shielding.

The potential for a rigidly fixed synthetic graft placed in the over-the-top position to be stress shielding/stress sharing with the patellar tendon autograft was assessed in a primate model. A patellar tendon autograft was placed anatomically and tensioned at 2 pounds for all of the groups. In the augmented animals, a 30 strand braided graft 10 cm in length of expanded polytetrafluoroethylene was tightened with the knee in full extension. After 6 months of unrestricted cage activity the animals were sacrificed and biomechanical testing performed. The augmented patellar tendon autografts demonstrated less laxity in extension as compared to the autografts alone. A minimal decrease in the load and stiffness to failure for the augmented groups as compared to the nonaugmented knees was noted. However, both the reconstruction groups had a significant decrease in the load to failure at 6 months (50% of the normal ACL). In summary, this study demonstrated that a synthetic graft augmentation can be performed in the over-the-top position and minimize knee laxity, especially during terminal extension. With this technique, the laxity was minimized while the incorporation and strengthening of the biologic autograft occurred at a rate similar to the unaugmented reconstruction.

Animals↗