PARECOXIB IMPAIRS EARLY TENDON REPAIR BUT IMPROVES LATER REMODELING

Background: Cyclooxygenase inhibitors may inhibit bone repair through their action on the bone morphogenic protein system – their effect on tendon repair is not known.

Research question/s: Do cyclooxygenase inhibitors negatively affect early tendon repair?

Methodology::Subjects: Eighty rats that underwent an Achilles tendon transection.

Experimental procedure: Rats were randomly allocated to the following study groups according to drug administration 6.4 mg/kg body weight parecoxib (PC) daily or placebo (PL) – saline), timing of administration, and timing of sacrifice (8–14 days post injury): (1) PL0-5 D8 (PL days 0–5 sacrifice day 8 = 9); (2) PA0-5 D8 (PC days 0–5 sacrifice day 8 = 10); (3) PL0-5 D8 (PL days 0–5 sacrifice day 14 = 10); (4) PA0-5 D8 (PC days 0–5 sacrifice day 14 = 10); (5) PL6-14 D14 (PL days 6–14 sacrifice day 14 = 10); (6) PA6-14 D14 (PC days 6-14 sacrifice day 14 = 10). Tissue was subjected to biomechanical testing and histological analysis on day of sacrifice.

Measures of outcome: Biomechanical data at failure: (force (N), stiffness (N/mm), energy (N.mm), area (mm²), stress (MPa)), histological callus tissue maturity.

Main finding/s:

• Day 8: early PC treatment caused a 27% decrease in force at failure (p  =  0.007), a 25% decrease in maximum stress (p  =  0.01), and a 31% decrease in energy uptake (p  =  0.05)

• Day 14: early PC treatment caused a decrease in stiffness (p  =  0.004), while late PC treatment caused …