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Biomedical subjects

R R Glisson

Publications and source records attributed to R R Glisson.

At least 37 records · Page 2Linked to original sources
PubMed1992

The effect of extracorporeal shock wave lithotripsy on the prosthesis interface in cementless arthroplasty. Evaluation in a rabbit model.

The effect of extracorporeal shock wave lithotripsy on interfacial strength between prosthesis and bone in cementless arthroplasty was examined using a rabbit model. Paired femora, each implanted with fiber mesh porous coated titanium implants, were harvested from rabbits 15 weeks after implantation. In group I, one femur from each pair was exposed to lithotripsy treatment consisting of 2,000 shocks at 20 kV. In group II, one femur from each pair was exposed to 2,000 shocks at 26 kV. Contralateral femora from each pair served as controls in both groups. Mechanical pushout tests were conducted on the implants using a 1321 Instron testing machine at a constant rate of 1 mm/minute. Shock waves generated at 20 kV were found to have no significant decrease on either the prosthesis/bone interfacial strength or energy to failure of cementless implants. Shock waves generated at 26 kV produced a mean 17.45% decrease in the prosthesis/bone interfacial strength, which approached statistical significance (P = .062), and a 7.84% mean decrease in the energy to failure (P = .268). However, in four of the seven group II specimens, cortical fractures occurred. These findings suggest that lithotripsy will not aid in the removal of uncemented porous coated devices and lithotripsy inadvertently focused at an uncemented device will not disrupt significantly the prosthesis-bone interface.

Animals↗
PubMed1992

The effect of femoral stem geometry on interface motion in uncemented porous-coated total hip prostheses. Comparison of straight-stem and curved-stem designs.

We compared the magnitudes of motion between the prosthesis and bone during axial and torsional loading in seven matched pairs of fresh-frozen femora of cadavera in which an uncemented, collarless, isthmus-filling, straight-stem (Harris-Galante) prosthesis had been placed in one femur and an uncemented, collarless, proximal-filling, curved-stem (anatomic) prosthesis had been placed in the other femur. The comparison was performed in order to determine the effect of the geometry of the stem on the magnitude of motion. Single-limb-stance loads and combined axial and torsional loads were applied to the implanted femoral prostheses with the use of a jig that simulated acetabular and trochanteric loading. Extensometers were used to measure motion at the prosthesis-bone interface. The prostheses were then removed and were reinserted, with cement applied to the proximal porous coating to simulate ingrowth of bone. The single-limb-stance and combined axial and torsional loads were reapplied and the magnitude of motion was recorded again. No significant differences in the magnitudes of the motion were found between the femora in which the straight stem had been implanted and the femora in which the curved stem had been implanted, during either simulated single-limb-stance or low-intensity torsional loading. When large torsional moments (twenty-two newton-meters) were applied, significantly less motion occurred at the bone-prosthesis interface, both proximally (p = 0.019) and distally (p = 0.0013), in the femora with the curved-stem implant than in the femora with the straight-stem implant. When cement had been applied proximally, proximal and distal motion between the prosthesis and the femur was decreased during simulated single-limb-stance and during torsional loading in the femora with the straight stem and the femora with the curved stem.

Adolescent↗
PubMed1991

Morphologic and morphometric analyses of rat femoral arteries after crush injury.

Replantation after crush amputation has a relatively low success rate. An arterial crush injury was produced in rats under a range of pressure (8.5 to 2,551 g/mm2) and durations (10 to 60 minutes). The degrees of vessel injury and thrombus formation were evaluated as functions of both crush force and duration, and the healing process was followed for 8 weeks. Crushing resulted in morphologic damage to the arterial wall but did not impair patency. Damage was directly proportional to crush pressure and duration. Intimal denudation caused flat platelet adhesion but no thrombus formation or thrombosis. Re-endothelialization was completed by 2 weeks. Intimal hyperplasia appeared at 1 week and consisted of endothelia in the most luminal layers and smooth muscle in the deeper layers. the internal elastic lamina was intact in all specimens and was thought to minimize platelet aggregation on the arterial wall after denudation of the intima.

Animals↗
PubMed1991

Prosthetic silicone scaphoid strains: effects of intercarpal fusions.

To assess stress shielding by partial intercarpal fusion, strains within a silicon scaphoid prosthesis were measured in five fresh upper extremities while the wrist was moved through a functional range of motion before and after capitate-lunate and capitate-hamate-lunate-triquetral intercarpal fusions. Capitate-lunate fusions resulted in an overall 18.4% reduction in compressive strains and a 10.8% reduction in tensile strains. Capitate-hamate-lunate-triquetral fusions reduced compressive strains by 28.5% and tensile strains by 26.3%. Radially deviated positions and positions of extension produced no reduction in strains with the partial fusions. Modest strain shielding can be obtained with partial intercarpal fusions. The effect, however, is position dependent, and whether this degree of strain shielding can reduce the incidence of particulate synovitis remains unknown.

Arthrodesis↗
PubMed1991

Screw-augmented fixation of acetabular components. A mechanical model to determine optimal screw placement.

Sixteen embalmed hemipelves were used to determine the optimal acetabular screw placement to provide maximal screw pull-out strength in unicortical and bicortical screw fixation. The anterior column, superior ilium, posterior column, ischium, and pubis regions of the pelvis were tested using 6.5-mm titanium alloy screws and a hydraulic servo-controlled 1321 Instron testing machine. Force vs displacement data were acquired. Bicortical fixation was stronger than unicortical fixation in the four zones compared. This difference was significant in the superior ilium, posterior column, and ischium. The anterior column could not accept unicortical screws due to inadequate bone depth, which ranged between only 6 mm and 10 mm. Bicortical fixation was significantly greater in the superior ilium, posterior column, and ischium than in the anterior column or pubis. Unicortical fixation was greatest in the superior ilium. This information may aid decisions concerning the positioning of screws to augment acetabular component fixation.

Acetabulum↗
PubMed1990

Kinematics of the ulnar carpus related to the volar intercalated segment instability pattern.

Anatomic dissections were done on 18 fresh and 4 preserved cadaver upper extremities to study the pathology of the carpal kinetics and to define the ligaments involved in the volar intercalated segment instability pattern. In a normal wrist, the scaphoid, lunate, and triquetrum all rotate so that their distal surfaces tilt palmarward with radial deviation. With ulnar deviation, all three carpal bones rotate dorsally. In the volar intercalated segment instability pattern, the lunate remains tilted volarly instead of rotating dorsally with ulnar deviation. In this study changes in carpal motion were observed after serially sectioning the ligaments supporting the ulnar carpus before and after loads were applied to the wrist to simulate the dynamic conditions of the wrist. The ligaments were then repaired to help identify which repairs restored normal carpal motion with radial and ulnar deviation with and without axial loads. In these anatomic studies the volar intercalated segment instability pattern occurred when there was instability between both hamate and triquetrum and between the lunate and triquetrum. The main ligaments involved in this instability appeared to be the ulnar half of the volar arcuate ligament and the luno-triquetral ligament as division of these ligaments, particularly under axial loads, produced the most significant change in lunate rotation (p less than 0.05). Similarly repair of these two ligaments produced the most significant correction of lunate position particularly with maintenance of dorsal rotation of the lunate during ulnar deviation under axial loads (p less than 0.01).

Humans↗
PubMed1989

Effect of hyaluronic acid/chondroitin sulfate on healing of full-thickness tendon lacerations in rabbits.

Viscoat, a high-molecular-weight, highly purified hyaluronic acid (HA) and chondroitin sulfate (CS) compound, was instilled around rabbit plantaris tendon following full-thickness laceration and surgical repair. After 3 weeks of immobilization, no significant difference in adhesion strength or tensile strength of the healing tendons existed between Viscoat-treated tendons and controls. This contradicts previous studies which suggest that hyaluronic acid reduces postoperative tendon adhesions. Further studies examining tendon adhesions after less severe degrees of tendon injury and using direct, quantitative measurement techniques are warranted to demonstrate whether HA has a beneficial effect on tendon healing.

Animals↗
PubMed1988

Immediate and delayed neurorrhaphy in a rabbit model: a functional, histologic, and biochemical comparison.

The effect of timing of neurorrhaphy on neuromuscular function was studied. The extensor digitorum longus neuromuscular units of 51 rabbits were used, with repairs performed immediately, 3 weeks, 3 months, and 6 months after nerve transection. Neuromuscular function was assessed 3 months after nerve repair, as was histology, histochemistry, and muscle hydroxyproline content. Force generated by immediately repaired units was 93% of unoperated controls. All functional delayed repairs produced approximately 50% of control force. Mild endomysial and perimysial fibrosis was present in the immediate neurorrhaphy group. Fibrosis was mild to moderate in the functional delayed repairs and moderate to severe in the nonfunctional repairs. Total and regional hydroxyproline content correlated to both function and timing of nerve repair. The data demonstrate that immediate repair of peripheral nerve lacerations gives the best functional recovery in this rabbit model. If immediate repairs are not performed in the rabbit, approximately 50% to 75% of normal function can be obtained when repairs are delayed for periods of 3 weeks to 6 months.

Animals↗
PubMed1988

Partial excision of the triangular fibrocartilage complex.

A cadaver model was used to evaluate the effect of partial excision of the triangular fibrocartilage complex (TFCC) on ulnar wrist kinetics. Excision of less than two thirds of the horizontal portion of the TFCC was found to have no statistical effect experimentally on forearm axial load transmission. This data supports, from a biomechanical standpoint, partial excision of the central portion of the TFCC--a procedure advocated clinically by some for treatment of a central TFCC perforation.

Biomechanical Phenomena↗
PubMed1987

Forearm force transmission after surgical treatment of distal radioulnar joint disorders.

To evaluate the effect of silicone replacement of the distal ulnar, hemiresection arthroplasty and the Darrach procedure on ulnar support of the carpus, changes in force transmission to the radius and ulnar were measured using load cells in axially loaded cadaver arms. Testing of the intact specimens in neutral position showed that an average of 17% of the axial load was borne by the ulna whereas the load decreased to 3.6% after silicone arthroplasty, to 2.4% after hemiresection arthroplasty, and to 1.0% after the Darrach procedure. Only by placing the silicone cap on the ulna to lengthen it by 4 mm did the ulna load become within 75% of that in the intact specimen. In the intact specimen, ulna loading increased with wrist extension and ulna deviation and decreased with flexion and radial deviation, while after the surgical procedures there was no significant change in ulna loading with wrist position.

Biomechanical Phenomena↗
PubMed1986

A biomechanical comparison of the methods for treating Kienböck's disease.

Reduction of lunate compression is thought to promote revascularization of the lunate in patients with Kienböck's disease. The decompressing abilities of ulnar lengthening, radial shortening, capitate-hamate fusion, and scaphoid-trapezium-trapezoid (STT) fusion were examined in axially loaded, whole arm specimens. Lunate strain was monitored by electronic strain gauges and found to be proportional to the axial load borne by the bone. The STT fusions and the procedures to alter relative radial and ulnar length were successful in relieving lunate loading throughout a functional range of wrist motion and forearm rotation, but the capitate-hamate fusion was ineffective. Only the STT fusion resulted in a significant decrease in wrist range of motion. Incremental ulnar lengthening and radial shortening revealed that approximately 2 mm of length change maximizes lunate decompression without greatly increasing the risk of disorders of the distal radioulnar joint and ulnocarpal impingement.

Biomechanical Phenomena↗
PubMed1986

Force transmission through the distal radioulnar carpal joint: effect of ulnar lengthening and shortening.

Although numerous surgical procedures are performed on the wrist joint, little has been written regarding the effect of these procedures on the biomechanics of the wrist. This study has been undertaken to examine the in vitro consequences of ulnar lengthening and shortening. We have measured the axial forces transmitted through the distal radius and ulna and the pressure distribution on the articulating surface of the radius and triangular fibrocartilage complex for the intact wrist, with ulnar lengthening and with ulnar shortening. Lengthening of the ulna by 2.5 mm in the intact wrist increased the force borne by the ulna from 18.4% to 41.9% of the total axial load. Shortening of the ulna by 2.5 mm decreased axial load borne by the ulna to 4.3%. Removal of the articular disc portion of the triangular fibrocartilage complex decreased the load on the intact ulna from 18.4% to 6.2%. The peak pressure at the ulnolunate articulation increased from 1.4 N/mm2 for the unaltered wrist to 3.3 N/mm2 when the ulna was lengthened by 2.5 mm. These results suggest that the biomechanics of the wrist joint can be dramatically altered with relatively small (2.5 mm) changes in ulnar length and by removal of the articular disc portion of the triangular fibrocartilage complex.

Biomechanical Phenomena↗
PubMed1985

The extensor retinaculum of the wrist: an anatomical and biomechanical study.

Through an anatomical and biochemical study, utilizing sixty-five cadaver specimens, the extensor retinaculum of the wrist was examined. It is a complex variable fibrous structure, whose functions are to prevent dorsal bowstringing of the extensor tendons and to prevent radial and ulnar displacement of extensor tendons. We recommend that a portion of the extensor retinaculum be preserved or reconstructed at the time of dorsal wrist surgery.

Biomechanical Phenomena↗
PubMed1985

A biomechanical analysis of spinal instrumentation systems in thoracolumbar fractures. Comparison of traditional Harrington distraction instrumentation with segmental spinal instrumentation.

A total of 61 biomechanical tests were performed on 25 cadaveric spinal segments to investigate the comparative strengths of three instrumentation systems: 1) conventional Harrington distraction instrumentation (HRI), 2) segmentally wired Harrington distraction rods, and 3) Luque segmental spinal instrumentation (SSI). In type I testing in which axial preload was applied to normal specimens, and then progressive rotation until ultimate failure followed, five of six Harrington systems failed at the bone-metal interface. In contrast, all six Luque SSI vertebral segments disrupted in a location removed from the bone-metal interface. In Type-II testing (six specimens) in which axial loading of experimentally produced unstable burst fractures was applied, the most stable fixation in resisting compressive loads was segmentally wired Harrington distraction rods (P less than 0.001). In Type-III testing (six specimens), there was axial preloading, then progressive rotation applied to translational fracture-dislocations and this showed that the ability to resist torsion was lowest with plain HRI, slightly improved by segmentally wired HRI, and the stiffest system was Luque SSI (P less than 0.05). The three methods of testing cadaveric segments provided a relevant laboratory model for investigation of spinal instrumentation systems in thoracolumbar fracture stabilization. The results compare favorably with other biomechanical studies, information derived from in vitro and ex vivo animal models and clinical experience with failures of fixation. The biomechanical advantages of segmentally wired Harrington distraction instrumentation in resisting axial loads seem to justify this method of fixation in unstable burst fractures. Similarly, the use of Luque segmental spinal instrumentation with L-rods coupled together is the best method of achieving rotational stability in translational injuries (fracture-dislocations). However, the above biomechanical considerations should be balanced against the increased operative time, more exacting technical expertise required, and possible risk of iatrogenic neurologic sequelae in implementing segmental fixation in unstable thoracolumbar fracture management.

Adolescent↗
PubMedDate not supplied

Stiffness of simulated radial neck fractures fixed with 4 different devices.

We performed a structural investigation of several fixation devices for radial head and neck fixation. Fourteen pairs of fresh-frozen human elbows were used to simulate unstable radial neck fractures fixed with each of the following plates: 2.0-mm T-plate, 2.0-mm blade plate, 2.7-mm T-plate, and 2.7-mm T-plate modified with a fixed-angle blade. The plate constructs were axially loaded in compression with a materials testing machine, and stiffness was calculated from a load-deformation curve. Through use of paired comparisons, the average stiffness of the modified 2.7-mm plate was found to be significantly greater than that of either 2.0-mm plate, whereas a trend was observed for increased stiffness of the modified 2.7-mm T-plate in comparison with the standard 2.7-mm T-plate. The results indicate that two important variables affecting construct stiffness are plate thickness and incorporation of a fixed-angle blade. Given these findings, the addition of a fixed blade to the 2.7-mm plate may improve the stability of fixation of comminuted radial neck fractures.

Adult↗