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)

Reconstruction of the digital pulley in the monkey using biologic and nonbiologic materials.

A-2 pulleys were replaced in the hand of the nonhuman primate; on the long/little fingers the pulleys were reconstructed with a woven nylon fabric (Nitex), and on the ring/index fingers the pulleys were reconstructed with fascia lata. The opposite unoperated hand served as a control. At 2, 3, and 6 months postoperative, the animals were killed to compare the function of the reconstructed pulleys with the control pulleys of the opposite digit. Using a tensile testing machine, two parameters, work of flexion and tendon excursion, showed that both pulley reconstructions permitted minimal tendon bow-stringing and had excellent gliding function. Both materials increased in strength over time to become stronger than the control pulley. Histologic examination showed no foreign body reaction to the Nitex; excellent fibrous ingrowth into the woven nylon was seen, which matured in time. The surface of the Nitex pulley facing the tendon developed and maintained a synovial-like gliding surface. The Nitex pulley compared favorably with the fascial pulley biomechanically and histologically; both reconstructed pulleys functioned well compared with normal pulleys.

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.

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.

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.

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.

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.

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.