One of the most common complications following surgery for midshaft clavicle fracture is nonunion/delayed union. Extracorporeal shock wave therapy (ESWT) is an alternative to promote new bone formation without surgical complications. To date, no literature has reported low-intensity ESWT (LI-ESWT) in delayed union of midshaft clavicle fracture.

We reported a 66-year-old Chinese amateur cyclist with clavicle delayed union treated with 10 sessions of LI-ESWT (radial, 0.057 mJ/mm², 3 Hz, 3000 shocks). No anesthetics were applied, and no side effects occurred. At the 4 mo and 7 mo follow-ups, the patient achieved clinical and radiographical recovery, respectively.

In conclusion, our findings indicated that LI-ESWT could be a good option for treating midshaft clavicular delayed union.

Clavicle fractures, 80% of which occur at the midshaft, are the most common injury in cyclists, and studies have reported a prevalence of 13%-16% in this population vs 2.6%-4% in the general population[1-3]. With numerous studies indicating an unsatisfactory outcome and a high nonunion rate following conservative treatment, an increasing trend has been seen toward operative fixation of displaced midshaft clavicle fractures[4]. Nonunions and delayed unions are common complications of clavicle fracture operations. A complication rate of 15% was reported in revision surgery for clavicle nonunion[5]. Extracorporeal shock wave therapy (ESWT) has emerged as a feasible alternative for treating delayed union. Compared with surgeries, ESWT has similar efficacy without surgical complications[6].

For bone healing, however, ESWT is mostly administered at middle-to-high energy (≥ 0.08 mJ/mm²) and in a focused pattern[7,8]. However, the clavicle is currently considered unsuitable for conventional ESWT due to its superficial anatomical site and proximity to the air-filled lung tissue, which creates large differences in acoustic impedance and offers considerable risks of lung injury[9]. To the best of our knowledge, no clinical literature has reported the use of low-intensity ESWT (LI-ESWT) in delayed union of clavicle fracture after internal fixation. Here, we present a case of delayed union of the clavicle in a cyclist after screw and plate fixation. After 10 sessions of LI-ESWT treatment at an outpatient clinic, the patient achieved a satisfying asymptomatic recovery and bone union as indicated by radiographs during follow-ups. Informed consent was obtained from the patient, and this study was approved by our ethics committee of our hospital (No. 2020-340).

Delayed union of midshaft clavicle fracture.

We used the shock wave device ShockMaster 500 (GymnaUniphy NV, Bilzen, Belgium) for treatment. LI-ESWT treatment utilized ultrasound-assisted localization, and local anesthesia was not required (Figure 2A and B). The patient received a total of 10 sessions with a 2-d interval between two sessions, and each session lasted for approximately 10 min. The therapeutic parameter was 0.057 mJ/mm², radial pattern, 3 Hz and 3000 strikes. No immobilization was required after any treatment.

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Figure 2 Illustration diagram of the treatment process, equipment and mechanism of low-intensity extracorporeal shock wave therapy for clavicle nonunion. A: Treatment of the current patient by a therapist without anesthetics; B: Illustration of shockwave device and applicator; C: Mechanism diagram of the potential risks of conventional shockwave treatment for clavicle nonunion; D: Mechanism diagram of superiority of low-intensity extracorporeal shock wave therapy treatment for clavicle nonunion. VEGF: Vascular endothelial growth factor.

At the 4-mo follow-up, the patient’s VAS was 0 mm in active and 10 mm in static, while the DASH scores of the patient decreased to 7. At the 7-mo follow-up, both the VAS and DASH scores of the patient had decreased to 0. The patient’s global assessment at the 7-mo follow-up was “much better.” During the whole follow-up process, the patient experienced no therapy-related complications.

Bridging callus and new bone formation on X-ray and CT were observed at the 4 mo follow-up and further enhanced at the 7 mo follow-up (Figure 1D-I). The patient was able to attend normal cycling training on his last visit, but doctors suggested that he avoid intensive exercise.

Delayed union of fracture is mostly defined as no signs of bone healing 3-6 mo after injury or operation on X-ray or CT scan[10,11]. The incidence of clavicle nonunion can be as high as 7.5% for operational treatment, and surgery to revise clavicle nonunion can have an even higher complication rate than the initial surgery[5]. Risk factors for nonhealing midshaft clavicle fractures are smoking, complexity of fracture, complete fracture displacement, advanced age, and female sex. Displacement seems to be the most likely factor[12]. The risk factors for the current patient, as he was informed before surgery, were complete dislocation of the initial fracture, smoking habit, and age. High-energy ESWT, since the first report of its application in bone nonunion by Valchanou et al[13] in 1991, has been proven to be as effective as surgical procedures but free of surgical side effects for the treatment of ununited fractures. To date, both guidelines and the literature have mostly applied middle-to-high-energy ESWT to treat nonunion[10,14-16]. Shockwave-promoted bone healing is associated with mechanically induced microfractures, periosteal detachment, and a complex spectrum of biomolecular reactions[17,18]. However, high-energy ESWT can have hazardous effects, such as soft tissue edema, cortical fractures, intraosseous bleeding, and even displacement of bone fragments to pulmonary vessels, with the risk of pulmonary embolism[19]. Similar cambium cell proliferation was seen in low energy flux density (EFD) compared with a high-energy setting, and shockwaves with lower EFD have more capacity to induce angiogenesis and improve tissue perfusion in target tissues through upregulation of vascular endothelial growth factor[20,21] (Figure 2C and D).

In superficial musculoskeletal disorders, LI-ESWT has proven to be more therapeutic in pain relief than high-energy ESWT[22]. Tam et al[23] suggested that low-intensity treatment with more shocks under the same total energy dose (intensity multiplied by number of shocks) was more favorable in enchaining periosteal cell activities. The study by Ke et al[24] showed that multiple sessions of ESWT had greater efficacy than single sessions from the perspective of the clinically cumulative effect. It should be noted that ESWT treatment for clavicle fracture is potentially risky for lung tissue damage, as suggested in animal experiments[25,26]. Moreover, high-intensity ESWT is often more costly and more likely to be performed in an inpatient setting, whereas LI-ESWT can be performed at an outpatient clinic by a therapist[27].

The criteria of LI-ESWT vary. Here, we defined ESWT as EFD < 0.08 mJ/mm², as in previous reports[27]. Five studies to date reported ESWT on delayed clavicle union or nonunion. Alkhawashki[28] reported one case of successful ESWT treatment of clavicle nonunion, but the treatment was high-energy ESWT conducted in a single session. Moretti et al[29] reported ESWT treatment of clavicle pseudoarthrosis with EFD of 0.22-1.10 mJ/mm². Kertzman et al[7] reported a failed case of radial ESWT treatment of a clavicle nonunion despite initial surgical fixation with two sessions of 0.18 mJ/mm² treatment. Vulpiani et al[30] and Carfagni et al[31] also reported clavicle nonunion treated with middle-to-high-energy ESWT, but the methods or results were not individually shown (Table 1). None of these studies mentioned side effects. We learned from these studies and used a lower dose administered over more sessions for our patient, which produced positive results with no side effects.

However, this was only a pilot study. Studies with a higher level of evidence must be conducted to verify our findings.

In summary, this report describes a novel LI-ESWT protocol to optimize the clinical efficacy for delayed union of clavicle fracture that had been treated with internal fixation. The findings of this study could be particularly useful for dealing with delayed union or nonunion of midshaft clavicle fractures.