Abstract
Healing of large tendon defects is challenging. We studied the role of collagen implant with or without polydioxanone (PDS) sheath on the healing of a large Achilles tendon defect model, in rabbits. Sixty rabbits were divided into three groups. A 2 cm gap was created in the left Achilles tendon of all rabbits. In the control lesions, no implant was used. The other two groups were reconstructed by collagen and collagen-PDS implants respectively. The animals were clinically examined at weekly intervals and their lesions were observed by ultrasonography. Blood samples were obtained from the animals and were assessed for hematological analysis and determination of serum PDGF level, at 60 days post injury (DPI). The animals were then euthanized and their lesions were assessed for gross and histopathology, scanning electron microscopy, biomechanical testing, dry matter and hydroxyproline content. Another 65 pilot animals were also studied grossly and histopathologically to define the host implant interaction and graft incorporation at serial time points. The treated animals gained significantly better clinical scoring compared to the controls. Treatment with collagen and collagen-PDS implants significantly increased the biomechanical properties of the lesions compared to the control tendons at 60DPI (P<0.05). The tissue engineered implants also reduced peritendinous adhesion, muscle fibrosis and atrophy, and increased ultrasonographical echogenicity and homogenicity, maturation and differentiation of the collagen fibrils and fibers, tissue alignment and volume of the regenerated tissue compared to those of the control lesions (P<0.05). The implants were gradually absorbed and substituted by the new tendon. Implantation of the bioimplants had a significant role in initiating tendon healing and the implants were biocompatible, biodegradable and safe for application in tendon reconstructive surgery. The results of the present study may be valuable in clinical practice.
Highlights
An Achilles tendon defect in the setting of large tissue loss is a more difficult problem than simple repair of a ruptured or lacerated tendon [1,2,3]
Clinical Findings The treated animals with Collagen-PDS prosthesis and those treated with collagen implant significantly gained better scoring number for tarsal flexion degree of the injured limb (18 (16–20) Collagen-PDS vs. 20 (18–24) Collagen vs. 27.5 (23–31) Control, P = 0.001, P = 0.049), heel and toe position of the injured limb (12 (9–14) Collagen-PDS vs. 14 (12–18) Collagen vs. 19 (17–22) Control, P = 0.001, P = 0.049), weight distribution on the legs (20 (16–25) Collagen-PDS vs. 22.5 (18–25) Collagen vs. 29 (26–32) Control, P = 0.001, P = 0.042) and pain on palpation (12 (11–15) Collagen-PDS vs. 14 (12–17) Collagen vs. 20 (18–24) Control, P = 0.001, P = 0.047) compared to those of the control animals
At 60 days post injury (DPI), the diameter of the ITTCs and ITTC-PDSs reached their normal level and there were no significant diffrences between these tendons at 60 DPI compared to those of the 0 DPI and their Normal contralateral tendon (NCT) (P.0.05 for all)
Summary
An Achilles tendon defect in the setting of large tissue loss is a more difficult problem than simple repair of a ruptured or lacerated tendon [1,2,3]. Due to many soft connective tissue tumors such as Xantoma, fibrosarcoma and liposarcoma, gangrenous and infective ulcers, burning, traumatic injuries (e.g. car accident or gunshot trauma), tendinitis or tendinopathy, and neglected Achilles tendon ruptures or chronic ruptures [1,3,4,5,6,7,8,9,10], large tendon defect could occur [6]. Tendon transplantation could be a potential method of choice; due to the large size of the harvesting autograft, the donor site morbidity is a major concern and the allografts due to many reasons such as disease transmission (e.g. HIV), rejection and ethical concerns, have not been widely accepted as yet [1,2,7] For these reasons treatment of such massive tendon injuries is a state of art and depends on the surgeon’s experience, equipment, facilitation, and condition [1,3,7]. Tendon healing has its own limitations such as development of peritendinous adhesion and muscle fibrosis and in those tendon injuries with significant tissue loss the natural healing response may not be able to replace the damaged tissue [3,5,14]
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