¹BG Klinik Tübingen, Clinic for Trauma and Reconstructive Surgery, Eberhards Karls University Tübingen, Tübingen, Deutschland
²Saarland University, Clinical-Experimental Surgery, Homburg, Germany, Homburg, Deutschland
³BG Klinik Tübingen, Clinic for Trauma and Reconstructive Surgery, Eberhards Karls University Tübingen, Homburg, Deutschland

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Objectives and questions: For the management of post-injury pain in aged patients Diclofenac, a nonsteroidal anti-inflammatory drug (NSAID), accounts to the most prescribed analgesic medications. However, NSAIDs negatively affect fracture healing. Additionally, recent research highlights potential differences in drug effects between male and female patients. Hence, we examined the effects of diclofenac treatment on fracture healing in aged male and female mice using a closed femoral fracture model.

Material and methods: In this study the influence of diclofenac on fracture healing was studied in aged CD-1 mice (16–18 months) using a femoral fracture model with intramedullary screw fixation. Treatment started the day of surgery. Mice received a daily dose of diclofenac (D) (intraperitoneal (i.p.) injection of 5 mg/kg body weight, male: n= 11, female n =14) or vehicle (C) (NaCl, male: n = 11; female n = 12) for durations of 2 and 5 weeks, respectively. Fracture healing was analyzed by X-ray imaging, biomechanics, micro-computed tomography (CT), histology and histomorphometry. Data are expressed as mean ± SEM. Statistical differences between the groups were assessed using Student’s t-test. Statistical significance was accepted for p<0.05.

Results: Our results showed a significant decrease in bending stiffness at 5 weeks post-surgery in aged male mice (D: 16.9% ± 4.0 vs. C: 53.1% ± 14.1 (p≤0.037) to contralateral femur). This reduction was less pronounced in aged female mice (D: 34.1 ± 7.1 in % vs. C: 46.9 ± 10.7 (p<0.0001) contralateral femur). These differences were associated with a lower amount of bone tissue and significantly higher amounts of fibrous tissue in the callus of aged male CD-1 mice. Furthermore, the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts within the callus was significantly higher in diclofenac-treated aged male mice at 5 weeks after surgery compared to controls (D: 3.7 ± 0.3 vs. C: 2.6 ± 0.3 (p=0.0242) osteoclasts/high power field (HPF)). Interestingly, this increase in the number of osteoclasts was not observed in aged female mice (D: 2.3 ± 0.5 vs. C: 2.9 ± 0.3 (p≤0.405) osteoclasts/HPF).

Discussion and conclusions: This study shows that male aged CD-1 mice suffer from a more pronounced impairment of fracture healing after diclofenac treatment when compared to female aged mice. This could be attributed to an excessive overshooting osteoclast response at the late stage of fracture healing in aged male mice. These findings indicate that diclofenac treatment in aged male patients should be avoided during fracture healing.