The long-term effects of extracorporeal shock waves on the epiphysis of the adolescent rat

Background

Extracorporeal shock waves (ESW) have been successfully used to treat musculoskeletal injuries, tendinopathy, and plantar fasciitis. Different side effects of high-energy ESWT on bones, tendons, nerves, epiphysis, and cartilage have been discussed. Although the effects of ESW on the epiphysis in animal models have been described, no studies have investigated the long-term effect of ESW on the immature epiphysis in an animal model. The purpose of this study was to investigate the long-term effects of ESW on the immature epiphysis in rats.

Methods

Sixteen 4-week old Wistar albino rats, average weight 116.3 grams (109.6–120.2 g) were used for these experiments. The rats were randomly divided into two groups, the ESW 1500 pulses (ESW1500p) group (n = 8) and the ESW 3000 pulses (ESW3000p) group (n = 8). In the ESW1500p group, 1500 pulses, at 4 bar, of 1-Hz shockwaves were applied, once, to the left knees of the rats. In the ESW3000p group, 3000 pulses, at 4 bar, of 1-Hz shockwaves were applied, once, to the left knees of the rats. The right knees (n = 16) of the rats in the two groups were used as the controls. The animals were sacrificed after an 8-month follow-up period. Femoral epiphyses were assessed by use of histology. The femoral length (FL), tibial length (TL), and femoral supracondylar medio-lateral width (MLW) were measured.

Results

There was no statistically significant difference between FL, TL, and MLW for the three groups (P > 0.05). The average histological scores were 8.8 (7–10), 17.8 (15–22), and 2.7 (0–4) in the ESW1500p, the ESW3000p groups, and the controls, respectively. The average histological score for the ESW3000p group was significantly higher than those for the ESW1500p group and the controls (P < 0.001). The average histological score for the ESW1500p group was significantly higher than that for the controls (P < 0.001).

Conclusions

The histological findings of this study indicate that ESW increased the cellularity and basophilia of the extracellular matrix (ECM) in the adolescent rat epiphysis and there were no negative effects on extremity measurements in the long term.