cis-hydroxyproline limits work necessary to flex a digit after tendon injury

A collagen prolyl 4-hydroxylase inhibitor reduces adhesions after tendon injury

Collagen synthesis inhibition potentially can reduce adhesion formation after tendon injury but also may affect cutaneous wound healing. We hypothesized that a novel orally administered collagen synthesis inhibitor (CPHI-I) would substantially reduce flexor tendon adhesions after injury, without any clinically important effect on cutaneous wound healing. The experiments were performed in a rat model with an in-continuity crush injury model in the rat hindfoot flexor tendon to provoke adhesion formation. Assays of dermal collagen production and the rate of healing of an excised wound were performed to assess cutaneous wound healing. Animals in the treatment groups received CPHI-I for 1, 2, or 6 weeks and were assessed at either 2 or 6 weeks. The work of flexion in the injured digit was reduced in the CPHI-I-treated animals compared with control animals, (0.188 J versus 0.0307 J at 2 weeks, and 0.0231 J versus 0.0331 J at 6 weeks) The cutaneous wound healing rate was similar in all animals, but dermal collagen synthesis was reduced in the treated animals. The CPHI-I seems to reduce tendon adhesion, and although collagen synthesis was reduced in cutaneous wounds, CPHI-I did not retard wound healing.

Efficacy of ADCON-T/N after primary flexor tendon repair in Zone II: a controlled clinical trial

A prospective double-blind, randomized, controlled clinical trial was conducted to assess the use of ADCON-T/N after flexor tendon repair in Zone II. Forty-five patients with 82 flexor tendon repairs in 50 digits completed the study. ADCON-T/N was injected into the tendon sheath after tenorrhaphy in the experimental group while the control group was not treated with ADCON-T/N. ADCON-T/N had no statistically significant effect on total active motion at 3, 6 and 12 months but the time taken to achieve the final range of motion was significantly shorter in treated patients. ADCON-treated patients had a higher rupture rate but this was not significant.

Palmar and digital flexor tendon pulleys

Retinacular structures, called pulleys, maintain the flexor tendons of the hand in constant relationship to the joint axes and promote economy and efficiency in finger flexion. This system is composed of the transverse carpal ligament, the palmar aponeurosis pulley, and the digital flexor pulley system. Of these three components, the digital pulleys are the most critical to finger flexion. In their normal state, these pulley components are ideal in all aspects including configuration and location, which accomodates a 260 degrees arc of motion without impingement and with minimum friction while at the same time using muscle tendon excursion that is well within the natural range of the muscle. An absent pulley results in an increased moment arm and requires increased tendon excursion to produce the same arc of motion. Because muscle excursion is not a limitless factor and is directly proportional to muscle fiber length, the effectiveness of tendon excursion is dependent on maintenance of the critical relationship between pulleys and the adjacent joints. Preservation and reconstruction of this system is based on knowledge of the anatomy and an understanding of the relative functional significance of each component of the system.

A biomechanical study of tendon adhesion reduction using a biodegradable barrier in a rabbit model

Adhesion formation associated with tendon surgery is a widespread problem in which a healing tendon becomes adherent via scar tissue to surrounding structures such as bone, muscle, skin, tendon sheath, or other tendons. A model is described in which adhesions were generated reproducibly between the plantaris and Achilles tendons of the rabbit using a partial tenotomy, a Bunnel suture, and immobilization. Using this model, the effect of an absorbable barrier, INTERCEED (TC7), on adhesion formation was investigated. This material, which is a fabric comprised of oxidized regenerated cellulose, was found to diminish significantly the extent and severity of intertendinous adhesions, assessed both mechanically and histologically. No evidence of a foreign body reaction was observed.

Efficiency of the flexor tendon pulley system in human cadaver hands

The efficiency of the flexor tendon system was examined in a human cadaver model. Pulleys were randomly sectioned, and the results were evaluated on the basis of the tendon excursion, force generated at the fingertip, and the work (force multiplied by distance) involved, as compared to the intact pulley system. When a single minor pulley (A1 or A5) was cut, there was no statistical difference in work efficiency or excursion efficiency from controls. Cutting all minor pulleys (A1, A3, A5) lead to a significant loss in excursion efficiency. The intact three pulley systems of A2, A3, and A4 were near normal and statistically better than A2 and A4 together for work efficiency. Cutting one of the major pulleys (A2, A4) resulted in significant changes in efficiency, but what was unexpected was to find an 85% loss of both work and excursion efficiency for the loss of A4 but only an excursion difference of 94% for the loss of A2. Our findings demonstrated that in this model, with the influence of the skin removed, A4 absence produced the largest biomechanically measured efficiency changes and that a combination of A2, A3, and A4 was necessary to preserve both work and excursion efficiency.

Mechanical analysis of the palmar aponeurosis pulley in human cadavers

The anatomy of the palmar aponeurosis pulley has been well described, but its biomechanical function is not as well characterized. This study describes the functional importance of the palmar aponeurosis pulley by using efficiency parameters. We obtained data by generating load, excursion, and work efficiencies in the intact pulley system and compared these to the efficiencies obtained after sectioning the palmar aponeurosis pulley alone and in combination with the proximal annular pulleys. The variability associated with comparisons between different fingers and hands was therefore diminished. Sectioning the palmar aponeurosis pulley alone did not significantly change any of the efficiency parameters. When the palmar aponeurosis pulley was sectioned in combination with either or both of the proximal annular pulleys (A1, A2) there was a significant decrease in excursion efficiency. Only after all three proximal pulleys were sectioned did the load efficiency increase and the work efficiency decrease significantly. These findings prove that the palmar aponeurosis pulley in combination with the proximal annular pulleys acts to decrease the tendency to bowstringing around the metacarpophalangeal joint. The increased load efficiency is probably the result of a decrease in friction and counteractive forces generated by the integrated fibers of the intact palmar aponeurosis pulley. Change in work is due not only to an increase in excursion, but also to the increased resistance that results from the acute angulation that the tendon must endure as it follows behind the remaining pulleys during flexion. Intergroup comparisons show a significant contribution by the palmar aponeurosis pulley. This study demonstrates a significant biomechanical role for the palmar aponeurosis pulleys and suggests that it be considered similar to the annular and cruciate flexor tendon pulleys in importance.

Biomechanical evaluation of chronic boutonnière reconstructions

The magnitudes of the extensor forces generated across the proximal interphalangeal joint by the Littler-Eaton, Matev, Hellmann, and Fowler reconstructive procedures for posttraumatic chronic boutonnière deformity were measured in a laboratory study. The purpose of the experiment was to determine whether the mechanical design of a procedure had a significant impact on biomechanical performance. Results showed that each method produced adequate extensor forces and restored full proximal interphalangeal joint extension. There were few statistically significant differences among the procedures for the different joint angles and load conditions tested. The data suggest that the mechanical designs of these reconstructions are satisfactory for correction of the extensor deficit of the deformity. The preoperative condition of the finger is probably responsible for the variations seen in clinical results.

Fracture disease and related contractures

Fracture disease and the complications of immobilization are described. The pathogenesis of the disease is discussed. The clinical implications of immobilization are outlined, and physical therapy modalities are reviewed. Also included is a summary of quadriceps contracture management.

An experimental model for the study of canine flexor tendon adhesions

An experimental model for the study of canine flexor tendon adhesions was designed using a standardized crush-abrasion injury, meticulous sheath closure, and three-week limb immobilization. Ten animals in the experimental protocol were evaluated for visible adhesion formation. With use of a flexor tendon adhesion rating scale, consistent adhesion formation was documented with an average score of 10.4 +/- 2.1 (range, 0 to 12). Five additional animals had biomechanical testing. Applying an increasing load to the proximally divided profundus tendon (0 to 10 Newtons), it was found that the angle of distal interphalangeal joint motion and the displacement of the toe were significantly decreased, and the work generated significantly increased in the experimental versus control digits (p less than 0.05). The consistent production of visible adhesions thus correlates with biomechanical impairments in toe motion and work. The study of agents aimed at diminishing flexor tendon adhesions will thus be facilitated by this reliable model. Systemic or intrasheath administration of agents will be possible.

Synthesis and characterization of magnetically responsive albumin microspheres containing cis-hydroxyproline for scar inhibition

Magnetically responsive albumin microspheres containing the proline analog, cis-hydroxyproline, were synthesized and their in-vitro physical properties were characterized. These microspheres have an average size of 1.1 +/- 0.3 microns with 94% of the microspheres less than 2.0 microns. They are uniformly spherical and contain 67% albumin, 22% magnetite, and 8% cis-hydroxyproline. The cis-hydroxyproline is releasable during a 72-h period and demonstrates a slow, releasable pool that constitutes approximately 50% of the incorporated drug. cis-Hydroxyproline is neither chemically nor biologically altered during its incorporation into the microsphere. cis-Hydroxyproline release from microspheres results in the in vitro inhibition of collagen secretion, which is indistinguishable from unincorporated cis-hydroxyproline. In a rat-tail animal model these microspheres were selectively targeted using an external magnetic field applied to a 1.5-2.0-cm target site. Fifty to 80% of the infused microspheres were localized to this site, whereas without a magnetic field only 15-20% of the microspheres are localized to this site. cis-Hydroxyproline microspheres resulted in a 16% decrease in collagen content in a scar model when compared with untreated animals (p less than 0.05). With further refinement of this method of drug delivery, clinically useful inhibition of scar formation may result.

Effects of indomethacin on adhesion formation after repair of zone II tendon lacerations in the rabbit

The flexor digitorum profundus tendon of the second medial toe of the hind foot was completely divided and repaired in zone II in 30 New Zealand white rabbits. Half of the animals received indomethacin solution (1 mg/kg/day) injected subcutaneously 2 hours before operation and daily for 4 weeks. The remaining 15 animals received daily injection of the same volume of saline solution. At 4 weeks the animals were killed and measurements were made of the angular motion of the distal interphalangeal joint and the excursion of the tendon. The animals treated with indomethacin had a greater tendon excursion and angular rotation of the joint than the control animals, implying a suppression of adhesions.

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)

Treatment of experimental silicosis with antifibrotic agents

We tested the efficacy of 2 antifibrotic agents, the proline analogue cis-4-hydroxy-L-proline (cHyp) and the lathyrogen beta-aminopropionitrile (BAPN), on experimental silicosis in hamsters. Silica (75 mg) was instilled intratracheally, and 3 months later lung hydroxyproline content, the volume density of silicotic nodules in lung parenchyma, fluid-filled lung pressure-volume curves, body weight and survival were measured. Animals were injected with cHyp, 200 mg/kg body weight, or BAPN, 150 mg/kg body weight, twice daily for 3 months. Hydroxyproline contents (mg/lung) at 3 months were: control, 0.8 +/- 0.1; silica, 1.4 +/- 0.1 (P less than 0.05 compared to control); silica-cHyp, 1.2 +/- 0.2; silica-BAPN, 1.4 +/- 0.1 (both NS compared to silica). The volume density of granuloma (% of surface area) was: silica, 0.7 +/- 0.1; silica-cHyp, 5.9 +/- 1.0; silica-BAPN, 9.7 +/- 1.5 (both P less than 0.5 compared to silica). There was no difference among the groups as assessed by lung pressure-volume curves. No toxic effects were produced on the skeletal system as assessed by bone hydroxyproline content and skeletal roentgenograms. Final body weights (g) were: silica, 114 +/- 5; silica-BAPN, 108 +/- 6; silica-cHyp, 88 +/- 7 (the latter P less than 0.05 compared to silica). Survival (%) was: silica, 62%; silica-BAPN, 34%, silica-cHyp, 28% (both P less than 0.05 compared to silica). These data show that cHyp and BAPN treatment did not prevent silica-induced pulmonary fibrosis, led to more extensive silicotic nodules, and were toxic. Both cHyp and BAPN have some efficacy in other models of fibrosis, and the observations in the present study could be specific to silicosis in the hamster.

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.

An apparatus to measure flexor tendon excursion and angular motion of the distal interphalangeal joint in a rabbit model

Investigators evaluating flexor tendon adhesions have utilized visual, histological, and gross mechanical methods in reporting their results. We have developed a device to measure tendon excursion and distal interphalangeal joint motion for a small animal model. The device was tested for accuracy and reproducibility using the rabbit hindfoot. There was no statistical difference between the right and the left in 30 pairs of feet. This device provides an accurate method to quantify tendon excursion and relative adhesion formation in a rabbit model without destroying the specimen.

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.

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.