Summary

This study suggests that focused extracorporeal shock wave therapy after intramedullary screw fixation for fifth metatarsal stress fractures in athletes may accelerate bone heeling and lead to an early return to original sports.

Abstract

Background

Intramedullary screw fixation is the most common treatment for fifth metatarsal stress fractures in athletes. On the other hand, focused extracorporeal shock wave therapy (ESWT) for bone promotes the production of various substances such as transforming growth factor-beta1, endothelial nitric oxide synthase, and vascular endothelial-derived growth factor, which play an important role in angiogenesis and bone formation. Therefore, it is widely used for the treatment of bone diseases such as delayed unions, non-unions and stress fractures in recent years. In addition, several reports have demonstrated that focused ESWT in treatment for stress fractures shortened the time to obtain bone union and the time to return to the original sport. However, to the best of our knowledge, there are no studies investigating the effect of focused ESWT in intramedullary screw fixation for fifth metatarsal stress fractures in athletes.

Purpose

To clarify the effect of focused ESWT in intramedullary screw fixation for fifth metatarsal stress fractures in athletes.

Methods

The authors retrospectively analyzed high-level athletes (Tegner activity score ≧ 7) who underwent intramedullary screw fixation using the Herbert type screw for fifth metatarsal stress fractures between April 2017 and August 2022. The minimum follow-up period of the patients was 2 years. The patients were divided into two groups: those treated intramedullary screw fixation combined with (group E) or without focused ESWT (group N), and the outcomes including the time to obtain bone union, the time to the original sport at the preinjury level and complications were statistically compared between the two groups. Focused ESWT were performed once a week, up to 4 times, from 2 weeks postoperatively, using 2500 impulses at an energy of 0.25 mJ/mm2 and 4Hz frequency.

Results

A total of 34 patients (31 men, 3 women, mean age 18.4 years) were included in this study. 13 patients were assigned to the group E, while 21 patients were assigned to the group N. There were no significant differences in the demographic characteristics of the patients between the two groups. The mean time to obtain bone union was 7.2 weeks in the group E, 9.3 weeks in the group N with significant difference (p < 0.001). Also, the mean time to return to the original sport was 9.1 weeks in the group E, 11.8 weeks in the group N with significant difference (p < 0.001). Although there were no complications in the group E, refracture occurred in one case of the group N. The complication rate was 0 % in the group E, 4.8 % in the group N with no significant difference (p > 0.05).

Conclusions

Although further studies with a lager sample size, longer follow-up period, and more rigorous designs are needed to verify outcome uniformity, focused ESWT after intramedullary screw fixation for fifth metatarsal stress fractures in athletes may accelerate bone heeling and lead to an early return to original sports.