A new model for experimental tendon adhesions in the chicken

Tendon Adhesions: A Novel Method of Objectively Measuring Adhesions by Assessing Tendon Glide Through a Soft Tissue Envelope in a Rat Model

PURPOSE

To develop a rat model of extra-synovial tendon adhesions that will enable accurate testing of scar barriers and adhesion inhibiting treatments to facilitate future research.

METHODS

Thirty-six 6-month-old male Sprague-Dawley rats were randomized to one of the 3 groups of 12. In Group A, the middle one-third portion of the left Achilles tendon was excised. In Group B, the tendon and soft tissue bed was abraded with steel wool. In Group C, a silk suture was sewn along the tendon. The right hind limbs served as controls. At 4 weeks, biomechanical testing was performed on the bilateral hind limbs. The Achilles tendon was cut at the gastrocnemius-tendon junction proximal to the "adhesion zone" (or analogous level in the control limb). The calcaneal insertion of the Achilles was attached to a tensiometer. The force needed to pull the tendon out of its soft tissue envelope at a fixed rate was measured.

RESULTS

Three rats were excluded because of complications during data collection. Pair-wise comparison testing was performed, comparing the mean peak force to pull the Achilles tendon from its soft tissue envelope in 33 control limbs and the contralateral limb from each group. The average peak force for the cut tendon group (A) was 20.1 N, 18.8 N in the steel wool group (B), and 21.1 N in the suture group (C). The average peak force in the control limbs was 15.6 N. There was a significant difference noted in peak forces between the control limbs and each experimental group.

CONCLUSIONS

A consistent and statistically increased force was necessary to pull a rodent Achilles tendon from an adhesion-induced tissue bed compared with controls. No statistical difference was detected between experimental groups.

CLINICAL RELEVANCE

Our study demonstrates an objective method of biomechanical tendon adhesion assessment in a rat model.

A mouse model of flexor tendon repair

Mouse models offer invaluable cellular and molecular tools for the study of human pathologies including those associated with fibrotic and musculoskeletal diseases. In this methods manuscript, we describe a mouse model of repair and segmental reconstruction of flexor tendons, which in our laboratory has been an invaluable model to study tendon scarring and adhesions. Specifically, we describe in details all the surgical procedures involved, as well as the associated endpoint biomechanical assessments including a novel test of the flexion of the metatarsophalangeal joint as a measure of adhesions, and a standard protocol for biomechanical assessment of the tensile strength of the tendon and repair tissue.

Cellular and molecular factors in flexor tendon repair and adhesions: a histological and gene expression analysis

Flexor tendon healing is mediated by cell proliferation, migration, and extracellular matrix synthesis that contribute to the formation of scar tissue and adhesion. The biological mechanisms of flexor tendon adhesion formation have been linked to transforming growth factor β (TGF-β). To elucidate the cellular and molecular events in this pathology, we implanted live flexor digitorum longus grafts from the reporter mouse Rosa26(LacZ/+) in wild-type recipients, and used histological β-galactosidase (β-gal) staining to evaluate the intrinsic versus extrinsic cellular origins of scar, and reverse transcription-polymerase chain reaction to measure gene expression of TGF-β and its receptors, extracellular matrix proteins, and matrix metalloproteinases (MMPs) and their regulators. Over the course of healing, graft cellularity and β-gal activity progressively increased, and β-gal-positive cells migrated out of the Rosa26(LacZ/+) graft. In addition, there was an evidence of influx of host cells (β-gal-negative) into the gliding space and the graft, suggesting that both graft and host cells contribute to adhesions. Interestingly, we observed a biphasic pattern in which Tgfb1 expression was the highest in the early phases of healing and gradually decreased thereafter, whereas Tgfb3 increased and remained upregulated later. The expression of TGF-β receptors was also upregulated throughout the healing phases. In addition, type III collagen and fibronectin were upregulated during the proliferative phase of healing, confirming that murine flexor tendon heals by scar tissue. Furthermore, gene expression of MMPs showed a differential pattern in which inflammatory MMPs were the highest early and matrix MMPs increased over time. These findings offer important insights into the complex cellular and molecular factors during flexor tendon healing.

Tendon adhesion measured by a video-assisted gliding test in a chicken model

We developed a video-assisted gliding test to evaluate the gliding force and the flexion angle with unrestricted joint motion. Tendon adhesion was induced in a chicken model of flexor digitorum profundus (FDP) injury at the annular pulley region of the long toe. The chicken feet were harvested immediately after injury, and 2 weeks and 6 weeks after injury. During the gliding test, the injured FDP was pulled for 15 mm then returned to its initial position. The test was recorded using a video camera and registered to the gliding test mechanical data. The maximum flexion angle and gliding resistance were calculated. The maximum flexion angle was significantly decreased from 78 (SD 10) in controls to 42 (SD 22) in tendons with injury, while gliding resistance was significantly increased in week 2 (0.06, SD 0.05) and week 6 (0.07, SD 0.01) after injury.

Corticosteroids as an adjunct to antibiotics and surgical drainage for the treatment of pyogenic flexor tenosynovitis

BACKGROUND

Many similarities exist between pyogenic flexor tenosynovitis and other closed-space infections such as septic arthritis. Previous studies have demonstrated that corticosteroids in conjunction with antibiotics considerably improve treatment outcomes in patients with septic arthritis. Using a chicken model, we investigated whether or not corticosteroids in combination with antibiotics and/or surgical drainage could minimize the loss of range of motion typically associated with pyogenic flexor tenosynovitis.

METHODS

We inoculated the flexor tendon sheath of the right long toe of broiler chickens with Staphylococcus aureus (American Type Culture Collection 29523 NA) (6 × 10(9) colony-forming units/mL) and twenty-four hours later administered one of six treatments to groups of fourteen or fifteen chickens. Treatment combinations included systemic or intrasynovial antibiotics, surgical drainage with catheter irrigation or no surgical drainage, and local corticosteroid injections or no corticosteroid injections. Measurements of active digital flexion at the proximal and middle interphalangeal joints were performed before inoculation and treatment and at seven, fourteen, and twenty-eight days after treatment. Flexion measurements were compared between groups as well as with similar measurements in the contralateral, uninfected, control long toe.

RESULTS

At twenty-eight days, two of three groups treated with locally administered corticosteroids and the group treated with intrasynovial antibiotics alone (without surgery) regained significantly more active flexion in comparison with chickens treated with systemic antibiotics and surgical drainage (the current standard of care). Pooled data revealed that the corticosteroid-treated groups regained significantly more active flexion at all post-treatment time points.

CONCLUSIONS

Our data support the hypothesis that adding locally administered corticosteroids to the treatment regimen for pyogenic flexor tenosynovitis in a chicken model can significantly decrease loss of motion resulting from the infection. Furthermore, locally administered antibiotics may be effective for the treatment of pyogenic flexor tenosynovitis.