Biomedical subjects

P A Lesker

Publications and source records attributed to P A Lesker.

At least 19 recordsLinked to original sources

PubMed1986

Effect of pulley excision on flexor tendon biomechanics.

Flexor tendon function following excision of various portions of the fibro-osseous pulley system was measured biomechanically using a tensile testing machine. The biomechanical parameters measured were tendon excursion (the excursion of the tendon required to fully flex the digit) and work of flexion (the area under the force-excursion curve, representing all the forces that resist tendon flexion). In this experiment, work of flexion included the forces necessary to accomplish full digital flexion against a 15-g counter-weight, as well as the frictional forces that resist tendon gliding. The results indicate that the work of flexion was affected to a greater degree by pulley loss than was tendon excursion, suggesting that it is a more sensitive measurement of tendon function. A2 was found to be the single most important pulley for flexor tendon function, followed by A4. However, both A2 and A4 had to be present if near-normal hand function was to be achieved; sacrificing the A1 pulley was not associated with a significant loss of flexion. The "pulley effect" of the skin and soft tissue as a supplement to the fibro-osseous pulleys in reducing tendon bow-stringing was also noted. Although the parameters of tendon excursion and work of flexion were used in this study to determine the effect of pulley loss on tendon function, they can also be used to evaluate other flexor tendon studies, such as pulley reconstruction.

Animals↗

PubMed1986

Effect of flexor sheath integrity on tendon gliding: a biomechanical and histologic study.

The effect on tendon gliding of flexor sheath excision versus incision/closure following primary flexor tendon repair was examined biomechanically and histologically in forty-one chickens. There was no significant difference in either the tendon excursion required to fully flex the digit or in the work of flexion (the integration of the forces that resist tendon gliding during excursion) between the sheath excised and sheath closed groups. The results were unaffected by postoperative immobilization or intermittent passive motion. Histologically, it was noted that at 3 weeks the healing tendon was surrounded by a layer of granulation tissue that was nearly identical in both the sheath excised and the sheath closed digits. Of note was the finding that a synovial lining could not be identified in those digits that had previously undergone sheath closure. However, at 6 weeks postoperatively, a new gliding surface could be identified surrounding the tendon in both the sheath excised and the sheath closed digits. This study indicates that closure of the flexor sheath after primary tendon repair does not improve tendon gliding as measured biomechanically. Despite its repair, the flexor sheath does not maintain its synovial characteristics as demonstrated histologically, and a new sheath must subsequently be formed.

Animals↗

PubMed1986

Continuous passive motion as an adjunct therapy for tenolysis.

A model was developed to evaluate continuous passive motion as an adjunct to tenolysis. The use of continuous passive motion after tenolysis was associated with a significant increase in tendon rupture and the terminal force necessary to flex the phalanx actively. Also, there was a decrease in the passive range of motion in the continuous passive motion group which appeared to be the result of increased granulation tissue which formed around tenolysed tendon.

Animals↗

PubMed1986

Development of a synthetic replacement for the flexor tendon pulleys--an experimental study.

A method was developed to reconstruct the fibro-osseous pulleys with Nitex, a synthetic material. Nitex is a closely woven fabric constructed from monofilament nylon fibers. Six adult monkeys (24 digits) had excision of the A1 and A2 pulleys; this was followed by reconstruction of the A2 pulley with the Nitex synthetic material. The animals were killed, two at a time, at 4, 8, and 12 weeks to evaluate the effectiveness of the Nitex pulleys. Flexor tendon function was assessed by biomechanical methods with a tensile testing machine to measure the tendon excursion and the work of flexion (the area under the force-excursion curve) necessary to fully flex each digit; these parameters revealed that the Nitex pulleys were capable of preventing tendon bow-stringing and did not significantly impair tendon gliding. The breaking strength of the Nitex pulleys was comparable to that of normal A2 pulleys (for monkeys weighing less than 10 kg) and it was sufficient to allow immediate mobilization of the digits postoperatively without fear of pulley rupture. Histologic examination showed minimal foreign body reaction around the Nitex, and the gliding surface of a Nitex pulley was found to be covered with a smooth layer of fibrous tissue with minimal adhesions to the underlying flexor tendon. The synthetic Nitex pulley appears to have the potential to function as an effective fibro-osseous pulley replacement.

Animals↗

PubMed1986

The effect of flexor sheath integrity on nutrient uptake by primate flexor tendons.

The effect of flexor sheath excision versus sheath incision and repair on the uptake of 3H-proline by profundus tendons in zone II was examined. Proline uptake was measured at 7 days in eight monkeys with intact flexor tendons (group I) and at either 3 or 7 days in eight monkeys with the tendons transected and repaired (group II). In both groups, the flexor sheaths of the digits of the right hand were excised, whereas those of the left hand were incised and repaired. For both the intact and the transected and repaired flexor tendons, it was found that 3H-proline uptake was not improved with sheath closure. The extracellular tissue fluid appeared to be capable of providing nutrients to the tendon in amounts equal to that of the synovial fluid. Therefore, closure of the sheath after primary flexor tendon repair does not appear to be necessary for tendon nutrition, according to the data obtained from experimental studies on the nonhuman primate.

Animals↗

PubMed1985

Nutrient pathways to extensor tendons of primates.

The nutrient pathways to the extensor tendon beneath the extensor retinaculum of young adult monkeys was investigated using hydrogen as tracer material. The results indicate that diffusion from the synovium is a more significant nutrient pathway than vascular perfusion from either the mesotendon or the longitudinal intratendinous vascular network.

Animals↗

PubMed1985

Intrinsic restoration of the flexor tendon surface in the nonhuman primate.

A pattern of restoration of the smooth gliding surface was noted in lacerated monkey flexor tendon segments maintained in a cell free tissue culture environment over a 9-week period. The epitenon fibroblasts proliferated and migrated into the laceration site, forming collagen fibers that bridged the defect. After the smooth tendon surface was restored, the epitenon cellular response diminished.

Animals↗

PubMed1985

Flexor tendon nutrition.

The concepts regarding nutrient pathways to flexor tendons within the digital sheath are reviewed. Historically, both diffusion and perfusion have been considered significant pathways to the flexor tendon. Theories of tendon healing and adhesion formation, as well as techniques employed by the surgeon in the repair of tendons, are based on these concepts.

Blood Vessels↗

PubMed1985

Flexor tendon healing.

Concepts of flexor tendon healing suggest that repair is accomplished both by extrinsic peripheral fibroblasts and by intrinsic fibroblasts from the tendon itself. Recent studies indicate that although peripheral adhesions are associated with tendon healing, they are not essential to the repair process.

Animals↗

PubMed1985

The effect of surgical dissection on regional blood flow to the ulnar nerve in the cubital tunnel.

Regional blood flow to the ulnar nerve within the cubital tunnel of nonhuman primates was determined before and after surgical dissection by use of the hydrogen washout technique. The results indicate that anterior transposition is associated with a significant decrease in regional blood flow to the ulnar nerve for a period of at least three days. This relative ischemia was not noted following arcuate ligament incision or after medial humeral epicondylectomy. Vascular injection studies showed an abundant extrinsic arterial supply to the ulnar nerve, especially just distal to the groove that was apparently compromised during the anterior transposition.

Animals↗

PubMed1985

The effect of flexor sheath integrity on nutrient uptake by chicken flexor tendons.

The effect of varying degrees of flexor sheath integrity (sheath excised, incised, or incised and repaired) on the uptake of 3H-proline by chicken flexor tendons in Zone II was studied. The tendons were either: normal and uninjured, lacerated and repaired, or uninjured except for vinculum longum ligation. Different degrees of sheath integrity did not influence the uptake of 3H-proline by the tendons. The tendon does not appear to be dependent on a synovial environment for nutrients and is capable of obtaining these nutrients by diffusion from the surrounding extracellular tissue fluid. Diffusion is the primary nutrient pathway to the flexor tendon in this area, because removing its major vascular attachment (i.e., the vinculum longum) did not effect proline uptake. Careful closure of the sheath with restoration of a synovial environment does not appear to be necessary for tendon nutrition.

Animals↗

PubMed1984

Flexor tendon repair in vitro: a comparative histologic study of the rabbit, chicken, dog, and monkey.

Flexor tendon healing in four different animal species was explored in a tissue culture system. Ninety percent transverse lacerations were made in 88 tendon segments obtained from rabbits, chickens, dogs, and monkeys. The tendons were removed from culture and studied by light and electron microscopy at intervals of 3, 6, 9, and 12 weeks. A characteristic sequence of repair including epitenon thickening, cellular differentiation, cell migration, and phagocytosis was seen in each of the repaired tendons. The endotenon cells of several animal tendons appeared to be synthesizing collagen. There was a consistent difference in the rate of healing between the four species. The rabbit tendons demonstrated nearly complete closure of the repair site by 12 weeks. A lesser response was seen in the chicken, followed by the dog and monkey. The differences in healing rate appeared to be due to the non-species-specific in vitro culture media. The in vitro flexor tendon culture system is particularly useful in studying the tendon repair responses of various species with the contributions of vascularity and synovial cells excluded.

Animals↗

PubMed1984

Effect of antigen-induced synovitis on the extensor tendons within the retinacular compartment of the dog.

Antigen-induced proliferative synovitis was produced within the extensor retinacular compartment of one forepaw of young littermate dogs. The extensor tendons within the synovitis compartment were compared with the tendons in control compartments of the opposite forepaw. At 7 days following challenge, the tendons from the proliferative synovitis compartment showed increased uptake of [3H]proline at 5 min after pulse labeling. At 7, 14, and 28 days following challenge, the tendons within the proliferative synovitis compartment showed a significant increase in metabolic activity compared with control tendons after radioactive labeling for 6 h, with no associated difference in total collagen content of the control and synovitis tendons. These results indicate an increase in protein synthesis and degradation by the synovitis-surrounded tendons.

Animals↗

PubMed1984

Biochemical evidence of flexor tendon participation in the repair process--an in vitro study.

Rabbit, dog, chicken and monkey flexor tendon explants were maintained for six weeks in vitro in organ culture media. Biochemical evidence of the intrinsic capacity of the explants to participate in the repair process is noted by an increase in DNA (i.e. cell number) and hydroxyproline (i.e. collagen content) of the cultured explants after six weeks on culture compared to the control specimens, as well as the incorporation of 3H Proline into the collagen molecule.

Animals↗

PubMed1984

A dynamic canine model of experimental hip dysplasia. Gross and histological pathology, and the effect of position of immobilization on capital femoral epiphyseal blood flow.

We produced a dynamic model of experimental hip dysplasia in growing puppies by cast immobilization of a single hind leg with the knee in extension. Serial roentgenographic studies demonstrated a progressive acetabular dysplasia with subluxation and eventually dislocation of the femoral head. A consistent finding in the dysplastic hip was significant hypertrophy of the ligamentum capitum femoris, both in length and in cross-sectional area. Quantitative studies of blood flow in the femoral head by the hydrogen-washout technique in normal and dysplastic hips demonstrated a significant decrease in blood flow to the dysplastic femoral heads. The dysplastic hips were then placed in various positions of immobilization and blood-flow determinations were repeated. The position of forced abduction significantly reduced circulation in the femoral head, whereas immobilization in flexion consistently resulted in the highest rate of blood flow in the femoral head. These experimental data indicate the potential ischemic hazards of immobilization in the forced abducted position in the treatment of congenital dislocation of the hip. Progressive degenerative changes developed in the articular cartilage of the dislocated joint, with severe reduction of safranin-O staining, fibrocartilaginous metaplasia, and hypocellularity. The degenerative changes in the acetabular cartilage were more severe than those in the femoral head. These findings further emphasize the importance of reducing the dislocated hip at the earliest opportunity in order to prevent irreversible degenerative changes.

Animals↗

PubMed1984

Intrinsic flexor-tendon repair. A morphological study in vitro.

UNLABELLED: Rabbit flexor tendons with a 90 per cent mid-section transverse laceration demonstrated the intrinsic capacity to participate in the repair process in the absence of extrinsic cell sources and without the benefit of nutrition from a circulating blood supply or the influence of synovial fluid. Two cellular processes were involved in the in vitro repair process: (1) phagocytosis occurred by differentiation of fibroblasts from the epitenon--the cells migrated into the repair site and removed cellular debris and collagen fragments, and (2) collagen synthesis occurred primarily within the endotenon cells. CLINICAL SIGNIFICANCE: The results of this experimental study support the concept that flexor tendons have the intrinsic capacity to phagocytize old collagen and synthesize new collagen fibrils. Consequently, clinical attempts to prevent or control the peripheral adhesions appear valid, since these adhesions do not appear to be an essential component of the repair process.

Animals↗

PubMed1983

Comparative nutrient pathways to the flexor profundus tendons in Zone II of various experimental animals.

The role of diffusion and vascular perfusion as nutrient pathways to Zone II of the flexor profundus tendon of various experimental animals was studied by measuring the uptake of tritiated proline by tendon segments. The uptake by the flexor profundus tendon of the chicken resembled the uptake by that of the monkey in that both diffusion and perfusion effectively provided nutrients to the tendon. In contrast, the uptake by the dog and rabbit profundus tendon differed from the primate; although the uptake by diffusion resembled that of the monkey, the uptake by vascular perfusion was poor. Clinical relevance. These results challenge the use of the dog and rabbit as appropriate experimental animals when vascular perfusion of the profundus tendon in Zone II is an essential component of study.

Animals↗

PubMed1983

Palmar aponeurosis pulley.

The transverse fascicular fibers and paratendinous bands of the palmar aponeurosis are positioned at the proximal margin of the flexor tendon sheath. These anatomic structures form a tunnel around the flexor tendon and appear to function as a palmar aponeurosis pulley in conjunction with the first and second annular pulleys of the digital flexor mechanism.

Finger Joint↗