Is resection of the tendon edge necessary to enhance the healing process? An evaluation of the expression of collagen type I, IL-1β, IFN-γ, IL-4, and IL-13 in the distal 1 cm of a torn supraspinatus tendon: part II

Abstract

Background: Type I collagen proin pro-in expression in a damaged supraspinatus tendon is thought to be dependent on the distance from the edge of the tear and the local expression of pro-inflammatory, anti-proliferative, and pro-proliferative cytokines. The study evaluates the expression of type I collagen, pro-inflammatory interleukin (IL) 1β, anti-proliferative interferon-γ (IFN-γ), and pro-proliferative IL-4 and IL-13 cytokines along a 1-cm section taken from the edge of a torn supraspinatus tendon. Three sections were taken: 3 mm distal to the tear, 3 mm proximal to the tear, and the 4-mm middle section between them.

Methods: Nine patients (average age, 58 years) were included in the study. All fulfilled strict inclusion criteria regarding tear morphology and reconstruction technique. Samples were taken from the ruptured supraspinatus tendon at the time of arthroscopic repair. Quantitative real-time polymerase chain reaction assay was used for analysis.

Results: The expression of type I collagen, IL-4, and IL-13 significantly increased and that of IL-1β and IFN-γ decreased from the distal to the proximal parts of the tendon edge (P < .05).

Conclusions: The expression of type I collagen is dependent on the distance from the edge of the torn supraspinatus tendon, the balance between anti-proliferative IFN-γ and pro-proliferative IL-4 and IL-13, and the expression of pro-inflammatory IL-1β. Hence, whereas resection of the distal 3 mm of the torn supraspinatus tendon edge eliminates its least valuable part, resection between 4 and 7 mm may enhance the healing process by reaching a reasonable compromise between the mechanical features of the tendon characterized by collagen type I expression and the technical abilities of reconstruction.

Keywords: Collagen type I; cytokines; supraspinatus tendon resection.