Abstract
Background
Focused extracorporeal shock wave therapy (F-ESWT) is widely used as a bone growth stimulator in the treatment of various bony injuries; however, no previous studies have specifically investigated the efficacy of F-ESWT following intramedullary screw fixation for Jones fractures in athletes.
Objective
To evaluate the efficacy of F-ESWT in promoting bone healing following intramedullary screw fixation for Jones fractures in high-level athletes.
Methods
This study retrospectively analyzed the treatment outcomes of intramedullary screw fixation using cannulated Herbert-type screws for Jones fractures between April 2017 and April 2023. All the study subjects participated in high-level sports activities (Tegner activity score ≥ 8) prior to injury. A total of 34 patients who met the inclusion/exclusion criteria were enrolled in the study. Among these subjects, 13 patients underwent F-ESWT as postoperative adjunctive therapy (ESWT group), while the remaining 21 patients underwent fracture fixation therapy without F-ESWT augmentation (Non-ESWT group). Application of F-ESWT to the fracture site was initiated at 2 weeks postoperatively and was repeatedly performed once a week for 3 to 4 sessions (administration of 2500 impulses; energy flux density of .20 to .25 mJ/mm2; frequency of 4 Hz). Based on clinical records, outcomes including the time to achieve bone union, the time to return to the original sport at the pre-injury level, and the presence of any treatment failures or complications were evaluated and statistically compared between the groups.
Results
All patients in both groups achieved bone union and returned to their original sports activities at their pre-injury level. The median time to obtain bone union was 8 [interquartile range (IQR), 6-8] weeks in the ESWT group and 10 [IQR, 8-10] weeks in the Non-ESWT group (P < .001). The median time to return to the participant's original sport was 9 [IQR, 8-10] weeks in the ESWT group and 12 [IQR, 10-12] weeks in the Non-ESWT group (P < .001). Only one case of refracture occurred in the Non-ESWT group; however, statistical analysis of treatment failures and complications revealed no significant difference between the two groups (P = 1.000).
Conclusion
The application of F-ESWT after intramedullary screw fixation for Jones fractures may be associated with earlier bone union and return to the original sport in high-level athletes. Further prospective studies with larger sample sizes, particularly randomized controlled trials, are needed to validate these preliminary findings.
Keywords: Bone healing, Fifth metatarsal stress fracture, Focused extracorporeal shock wave therapy, Intramedullary screw fixation, Jones fracture, Return to sport
1. Introduction
Proximal fifth metatarsal fractures are generally classified into three types according to the anatomical classification by Lawrence and Botte.1 Zone 1 fractures are acute avulsion fractures at the tuberosity of the fifth metatarsal. Zone 2 fractures are acute fractures at the metaphyseal-diaphyseal junction, defined as a Jones fracture. Zone 3 fractures are stress fractures in the proximal diaphyseal. However, because distinguishing between zone 2 and 3 fractures is difficult in clinical practice, most previous related studies have collectively referred to these two types of fractures as Jones fractures and analyzed them as a unified group. Consequently, both have been managed with the same treatment approach and have yielded similar outcomes.2, 3, 4 In the present study, zone 2 and 3 fractures will be collectively referred to as Jones fractures and the study contents will be discussed.
Jones fractures are a relatively common injury among athletes in sports requiring repetitive pivoting or rotational movements.5 Due to several factors, including poor blood supply and complex loading concentrated at the fracture site,6,7 Jones fractures are difficult to heal, and non-surgical treatment carries a significantly higher risk of delayed union, nonunion, and refracture.8,9 In addition, a recent systematic review has shown that surgical treatment yields superior outcomes compared to non-surgical treatment, including higher bone union and return-to-sports rates, shorter bone union and return-to-sports duration, and higher functional outcomes.10 Therefore, surgical treatment is generally recommended, especially for athletes. Among the various surgical techniques used to treat Jones fractures, intramedullary screw fixation has become the primary treatment option based on the findings of relevant research, with favorable outcomes reported, including a nearly 100 % return-to-play rate.2, 3, 4,9,11,12 However, the time of return-to-play reported in previous studies averages 9.6 weeks,10 which falls short of the demands of high-level athletes who wish to return to sports as early as possible. Furthermore, it has been reported that return-to-play before adequate bone union is achieved can lead to surgical failures, such as delayed union or refracture.13,14 Therefore, supplementary measures for intramedullary fixation to promote fracture healing have become a clinically significant challenge.
Recently, several clinical studies have evaluated the efficacy of various adjunctive therapies such as autologous bone grafting, bone marrow aspirate concentrate (BMAC), and low-intensity pulsed ultrasound (LIPUS) in the surgical management of Jones fractures.3,4,14, 15, 16 However, the previous reports have concluded that none of these adjunctive therapies shorten the time to bone union or to return to sports in surgical fixation of Jones fractures.15,16 On the contrary, invasive adjunctive therapies, particularly autologous bone grafting and BMAC, may cause complications at the donor site and potentially delay the progress of postoperative rehabilitation.17
Extracorporeal shock wave therapy (ESWT) in current orthopaedic practice is predominantly applied for the treatment of overuse injuries18; however, in recent years, this modality has been additionally utilized as a bone growth stimulator.19 The clinical application of ESWT as a bone growth stimulator was first introduced by Valchanou et al.20 Since then, several clinical studies have investigated the therapeutic efficacy of ESWT, especially focused ESWT (F-ESWT), for various bone disorders, including delayed union, nonunion, and stress fractures, reporting satisfactory results.21, 22, 23, 24, 25, 26, 27, 28, 29, 30 In addition, a recent experimental study has demonstrated that F-ESWT may exert a greater influence on bone biology during the fracture healing process compared to LIPUS.31 Therefore, applying F-ESWT as an adjunctive therapy after surgery may potentially promote bone healing. However, to our knowledge, no prior studies have specifically investigated the efficacy of F-ESWT following intramedullary screw fixation for Jones fractures in athletes.
The purpose of this study was to evaluate the efficacy of F-ESWT following intramedullary screw fixation for Jones fractures in high-level athletes. We hypothesized that F-ESWT following intramedullary screw fixation would facilitate earlier bone union and return to sports compared to intramedullary screw fixation alone.
2. Materials and methods
2.1. Study population
The design of this retrospective comparative study was approved by the institutional review board (approval number 4932). Data were obtained via individual patient records at the authors’ institution. The initial study population comprised of a consecutive series of high-level athletes with a Tegner activity scale ≥ 8 who underwent intramedullary screw fixation for Jones fractures between April 2017 and April 2023. Exclusion criteria were a postoperative follow-up period of less than two years and a history of prior surgery on the affected lower limb. All surgical procedures, perioperative management, and primary clinical and radiological evaluations were performed by a single orthopaedic surgeon.
2.2. Operative technique
All patients underwent intramedullary screw fixation using a Herbert-type screw following the surgical sequence described by Morimoto et al.2 First, a 1.6-mm guidewire was inserted percutaneously through the medullary cavity from the base of the fifth metatarsal toward the distal medial cortex under fluoroscopic guidance. A straight incision of approximately 1 cm in length was then made at the guidewire insertion site and drilling was performed with a cannulated drill passing through the fracture site. The diameter of the screw was determined based on the preoperative assessment on computed tomography (CT) images, and the length was determined by intraoperative measurement using a guidewire inserted into the medullary and a depth gauge. The Herbert-type screw was then inserted along the guidewire so that the distal thread contacted the inner wall of the distal medial cortex and the proximal thread was fully embedded in the base of the fifth metatarsal (Fig. 1). In none of the cases were adjunctive procedures performed for the purpose of biological augmentation, such as autologous bone grafting or BMAC.
Fig. 1.
(a) First, a 1.6-mm guidewire was inserted percutaneously through the medullary cavity under fluoroscopic guidance, from the base of the fifth metatarsal toward the distal medial cortex under fluoroscopic guidance. (b) A straight incision of approximately 1 cm was made at the guidewire insertion site and drilling was performed with a cannulated drill passing through the fracture site. (c) The cannulated Herbert-type screw was inserted following the guidewire so that the distal thread contacted the inner wall of the distal medial cortex while the proximal thread was fully embedded in the base of the fifth metatarsal.
2.3. Postoperative management
After surgery, a non-weight bearing short leg splint was applied for 2 weeks. After the splint was removed, active and passive range of motion exercises of the ankle and gradual progression of weightbearing were initiated at 2 weeks postoperatively. Patients were allowed to start jogging once callus formation at the fracture site was detected via radiographs. Subsequently, once complete bone union was confirmed by radiographs and physical examination revealed no tenderness at the fracture site, rehabilitation was progressively advanced to running, jumping, landing, cutting movements, sport-specific exercises, and participation in team practice, provided that the patients remained asymptomatic. Thereafter, patients were permitted to return to their original sport without restriction. Orthotic devices such as insoles were not applied in any of the included cases.
According to our standard postoperative follow-up protocol, all patients were scheduled to undergo clinical and radiographic evaluations at two-week intervals until they returned to their original sport at their pre-injury level. Thereafter, follow-up visits were conducted every 3 months. Although the exact timing of some follow-up visits varied slightly because of scheduling constraints, all deviations from the scheduled follow-up were within a few days. At each follow-up visit, patients underwent physical examination and standard anteroposterior, lateral, and oblique radiographs of the foot.
2.4. Postoperative F-ESWT
During the study period, all patients were informed about the possibility of F-ESWT application and its potential benefits. Only those who opted for the procedure received F-ESWT after surgery. F-ESWT was initiated at 2 weeks postoperatively and applied once a week to the fracture site using the DUOLITH SD-1 T-TOP Ultra (Storz Medical AG, Tägerwilen, Switzerland). Four weekly sessions were routinely planned; however, some patients received only three sessions because of scheduling constraints. The number of sessions was not determined based on clinical or radiographic evaluations. In addition, F-ESWT was performed at 2500 impulses, an energy flux density of .20 to .25 mJ/mm2, and a frequency of 4 Hz. These F-ESWT parameters were based on the standardized clinical protocol routinely used at our institution rather than on a specific previously published protocol. To determine the location of exposure, the fracture site was identified using ultrasound prior to each F-ESWT session (Fig. 2).
Fig. 2.
The fracture site (white arrow) was identified using ultrasound (a) and focused extracorporeal shock wave therapy was performed (b).
2.5. Data acquisition and analysis
Clinical data for the study population including age, sex, affected side, sport, Tegner activity scale, follow-up duration, fracture location, fracture type, fixation screw diameter and length, fifth metatarsal length, screw length ratio and intraoperative plantar gap widening at the fracture site were extracted from the medical records. Radiographic evaluation was used to identify the fracture location of the proximal fifth metatarsal based on the anatomical fracture classification as described by Lawrence and Botte, and fracture type was determined according to the Torg classification.1,32 The fifth metatarsal length was defined as the distance from the center of the fifth metatarsal base to the center of the articular surface of the metatarsal head on the preoperative anteroposterior foot radiograph. Screw length ratio was defined as the ratio of the length of the screw used to the fifth metatarsal length.2 Based on the study by Lee et al. intraoperative plantar gap widening was defined as an increase in the gap width on an oblique radiograph of the foot in an immediate postoperative radiograph compared with a preoperative radiograph.33 Postoperative bone union was defined as the disappearance of the fracture gap on anteroposterior, lateral, and oblique radiographs of the foot. In the cases where determining union based solely on radiographs was difficult, CT was performed to critically assess the status of bone union.3 This indication for CT was consistently applied throughout the study period. All radiographic images used for the primary outcome assessment were evaluated by a single orthopaedic surgeon who was not blinded. To evaluate the reliability of radiographic bone union assessment, all postoperative plain radiographs were independently reassessed by two orthopaedic surgeons who were not involved in the surgical procedures. Both reviewers were blinded to treatment allocation, the original assessment of bone union, and CT findings.
Outcome measures analyzed in this study were time to obtain bone union at the fracture site, time to return to the original sport, and treatment failures or complications. The time to return to the original sport was defined as the period from surgery to participation in at least one game at the patient's pre-injury level in their original sport. Treatment failures such as delayed union, nonunion, and refracture as well as complications such as infection, delayed wound healing, and sural nerve injury/irritation were also examined based on clinical records during the study period.
In the data analysis, the study population was divided into two groups based on the use of F-ESWT after intramedullary screw fixation: those treated with or without F-ESWT application (ESWT group and non-ESWT group). Subsequently, intergroup comparison was statistically conducted. In addition, subgroup analyses comparing clinical outcomes between zone 2 and 3 fractures within each group were conducted to assess whether it was appropriate to combine and analyze the data for these two fracture locations.
2.6. Statistical analysis
Statistical analysis was performed using JMP (Version 19; SAS Institute Inc). A P value < .05 was considered to be statistically significant. Continuous variables such as age, Tegner activity scale, follow-up duration, fifth metatarsal length, screw length ratio, intraoperative plantar gap widening, time to obtain bone union, and time to return to the original sport were presented as median [interquartile range (IQR)]. The Mann-Whitney U test was used to compare these continuous variables. Sex, affected side, sport type, treatment failures and complications were compared using Fisher's exact test. Differences in fracture location and Torg classification were evaluated using the chi-squared test. Interobserver reliability for the assessment of time to obtain bone union was evaluated using the intraclass correlation coefficient (ICC) based on a mixed-effects model, with case treated as a random effect and reviewer as a fixed effect. A priori power calculation for the required sample size was not conducted. A post-hoc power analysis with α = .05 was performed using the obtained data on time to achieve bone union using G*Power software (Version 3.1.9.6; Heinrich-Heine-Universität Düsseldorf).
3. Results
Of the 37 patients initially enrolled, 2 patients with a follow-up period of less than 2 years and one patient with a previous history of surgery on the affected lower extremity were excluded from the study. Of the remaining 34 patients, 13 patients were included in the ESWT group and 21 were included in the Non-ESWT group. Among the 13 patients in the ESWT group, 3 patients received three F-ESWT sessions because of scheduling constraints, whereas the remaining 10 patients completed all four sessions. No significant differences in clinical characteristics were observed between the two groups (Table 1).
Table 1.
Comparison of patient characteristics between the ESWT and Non-ESWT groups.
| Characteristics | ESWT group (n = 13) | Non-ESWT group (n = 21) | P Value |
|---|---|---|---|
| Age, yearsa | 17 [16-21] | 18 [16-20] | .728 |
| Sex, male/female, n | 13/0 | 18/3 | .270 |
| Affected side, right/left, n | 7/6 | 9/12 | .725 |
| Sports, n | .709 | ||
| Soccer | 12 | 18 | |
| Futsal | 1 | 2 | |
| Hockey | 0 | 1 | |
| Tegner activity scalea | 9 [9-9] | 9 [9-9] | .728 |
| Follow-up duration, monthsa | 30 [24-48] | 30 [24-38] | .913 |
| Fracture location, zone 2/3, n | 8/5 | 12/9 | 1.00 |
| Torg classification, Ⅰ/Ⅱ/Ⅲ, n | 4/7/2 | 5/10/6 | .669 |
| Screw diameter (mm), 4.5/5.0, n | 4/9 | 13/8 | .157 |
| Screw length (mm), 50/55/60, n | 1/9/3 | 2/15/4 | .952 |
| Fifth metatarsal length, mma | 76 [70-78] | 74 [71-76] | .249 |
| Screw length ratioa | .72 [.71-.79] | .74 [.72-.78] | .708 |
| Intraoperative plantar gap widening, mma | 1.5 [1.4-1.9] | 1.7 [1.5-1.8] | .929 |
ESWT; extracorporeal shock wave therapy.
Values are expressed as median [interquartile range].
All patients, irrespective of the group, achieved bone union and subsequently were able to return to their original sport at their pre-injury level (Fig. 3). CT to confirm bone union was required in 7 of the 34 patients (20.6 %), all of whom attained bone union at the corresponding time point. Interobserver reliability for the assessment of time to obtain bone union was excellent, with an ICC of .908. The outcomes of this study are shown in Table 2. In addition, the distributions of time to obtain bone union and time to return to sport in both groups are shown in Fig. 4. Time to obtain bone union and time to return to sport were significantly shorter in the ESWT group than in the Non-ESWT group. No treatment failures or complications were observed in the ESWT group, whereas one case of refracture was reported in the Non-ESWT group. However, statistical analysis of treatment failures and complications revealed no significant difference between the two groups. The refracture case in the Non-ESWT group was treated with revision intramedullary screw fixation using a larger-diameter Herbert-type screw. Bone union was achieved at 10 weeks postoperatively, and the patient returned to their original sport at 12 weeks postoperatively.
Fig. 3.
Pre- and post-operative radiographs from cases in the (a,c) ESWT group and (b,d) Non-ESWT group. At 6 weeks postoperatively, a bone union was obtained in a case of the ESWT (e), but it was not obtained in a case of the Non-ESWT group (f). Bone unions were confirmed in both the (g) ESWT and (h) Non-ESWT groups at 12 weeks postoperatively.
Table 2.
Comparison of outcomes between the ESWT and Non-ESWT groups.
| ESWT group (n = 13) | Non-ESWT group (n = 21) | P value | |
|---|---|---|---|
| Time to obtain bone union, weeksa | 8 [6-8] | 10 [8-10] | < .001 |
| Time to return to sport, weeksa | 9 [8-10] | 12 [10-12] | < .001 |
| Treatment failures/complications, n | 0 | 1 | 1.00 |
ESWT = extracorporeal shock wave therapy.
Values are expressed as median [interquartile range].
Fig. 4.
Distribution of (a) time to obtain bone union and (b) time to return to sport in the ESWT and Non-ESWT groups.
In the subgroup analysis examining the impact of fracture location on outcomes, no significant differences in outcome parameters were observed between zone 2 and 3 fractures within each group (Table 3).
Table 3.
Comparison of outcomes between zone 2 and zone 3 fractures in each group.
| ESWT group |
P value | Non-ESWT group |
P value | |||
|---|---|---|---|---|---|---|
| Zone 2 fracture (n = 8) | Zone 3 fracture (n = 5) | Zone 2 fracture (n = 12) | Zone 3 fracture (n = 9) | |||
| Time to obtain bone union, weeksa | 8 [6.5-8] | 6 [6-8] | .225 | 8 [8-10] | 10 [8-12] | .631 |
| Time to return to sport, weeksa | 10 [8.3-10] | 8 [8-9.5] | .152 | 12 [12-13.5] | 12 [10-13] | .496 |
ESWT = extracorporeal shock wave therapy.
Values are expressed as median [interquartile range].
4. Discussion
The most important finding of this study was that the use of F-ESWT after intramedullary screw fixation of Jones fractures in high-level athletes may be associated with earlier bone union and return to the original sport.
Jones fractures can be difficult to heal because of poor blood supply and complex loading concentrated at the fracture site.1,6,7 As a result of these unfavorable conditions for fracture healing, non-surgical treatment for Jones fractures may not achieve satisfactory outcomes, with a systematic review reporting an average return to sport rate of 71.6 %.10 In contrast, surgical fixation has been reported to yield a high return-to-sports rate exceeding 90 %, and is therefore recommended as the primary treatment option.10 Among various methods of fixation, intramedullary screw fixation is currently the most widely used technique in clinical practice, based on supportive results reported in relevant biomechanical and clinical studies. 2, 3, 4,9,11,12 There have been a number of studies examining the outcome of intramedullary screw fixation.2, 3, 4,9 Those studies have uniformly reported a high return-to-sports rate; however, the average time of return-to-sports is 9.6 weeks,10 which may not meet the expectations of high-level athletes hoping for the earliest possible functional recovery. In addition, an early return-to-sports before complete bone union is achieved may cause delayed union or re-fracture.13,14
Several adjunctive techniques have been proposed and evaluated for promoting bone union in the surgical fixation of Jones fractures.3,4,14, 15, 16 As biologic augmentation methods, autologous bone grafting and BMAC have traditionally been used in conjunction with fixation procedures for Jones fractures.3,4,14 Several clinical studies have evaluated the efficacy of autologous bone grafting in intramedullary screw fixation for Jones fractures.4,14 However, autologous bone grafting carries a risk of donor-site morbidity and complications such as infection, fracture, and neurologic injury, and its benefits are currently unknown.17,34 In addition, Murawski et al. have analyzed the efficacy of BMAC as a biologic enhancer rich in hematopoietic and mesenchymal stem cells, which play an important role in bone regeneration.3 They treated 26 athletes with intramedullary screw fixation and adjunct BMAC application. In this study, the mean time to obtain bone union was 5 weeks, suggesting the efficacy of BMAC as an adjuvant therapy to intramedullary screw fixation for Jones fractures. On the other hand, LIPUS is a non-invasive adjunctive therapy, which is widely used as a bone growth stimulator for various bone injuries.35 Murakami et al. have investigated the efficacy of LIPUS in intramedullary screw fixation for Jones fractures.16 When comparing treatment outcomes between the group that received LIPUS after intramedullary screw fixation and the group that did not, no significant difference was observed between the two groups in the time to obtain bone union.
Recently, F-ESWT has gained recognition as a bone growth stimulator and is widely used for the non-invasive treatment of various bone disorders.21, 22, 23, 24, 25, 26, 27, 28, 29, 30 Several basic studies have investigated the biological effects of ESWT on fracture healing. Previous experimental studies have suggested that extracorporeal shock wave may promote bone healing through biological effects involving angiogenesis, osteogenic differentiation, and bone regeneration.36, 37, 38, 39, 40 Importantly, the potential interaction between F-ESWT and the intramedullary screw remains unclear. The presence of a metallic implant may influence the propagation and local distribution of shock-wave energy; however, this interaction was not evaluated in the present study. Further biomechanical studies are needed to determine whether intramedullary screws affect shock-wave transmission to the fracture site. While research on the use of F-ESWT for Jones fractures is limited, some clinical studies have reported favorable outcomes.21,24,26 Alvarez et al. treated 34 cases of delayed union or nonunion of Jones fracture with F-ESWT and analyzed its treatment outcomes.21 In this report, radiographs taken at 12 weeks after F-ESWT application showed a bone union rate of 93.5 % (bone union was defined as either complete or partial bone union). Also, Furia et al. retrospectively compared the outcomes of F-ESWT versus intramedullary screw fixation for nonunion of Jones fractures.24 Among the 23 cases treated with F-ESWT, 20 cases (87.0 %) achieved bone union at 3 months, whereas among the 20 cases treated with intramedullary screw fixation, 18 cases (90.0 %) achieved bone union at 3 months. This confirms that both F-ESWT and intramedullary screw fixation are effective treatments for nonunion of Jones fractures. In 2023, Ramon et al. analyzed the treatment outcomes in a pilot randomized controlled trial involving 18 soccer players (9 with intramedullary screw fixation and 9 with conservative treatment with F-ESWT).26 They reported that pain relief, bone union rate, and time to return to sports were comparable between the two groups. Those previous studies have shown that noninvasive ESWT is as effective as surgical fixation in treating Jones fractures. However, the application of ESWT reported in the literature has been limited to its use as a standalone treatment in conservative management, and its efficacy as an adjunctive therapy in surgical treatment remains unclear.
To our knowledge, the present study is the first to investigate the efficacy of F-ESWT after intramedullary screw fixation for Jones fractures in high-level athletes. In our study, the time to obtain bone union and the time to return to sport were shorter in the ESWT group than in the Non-ESWT group. These results suggest that F-ESWT after intramedullary screw fixation may be associated with earlier bone union and return to the original sport. Notably, the outcomes in the ESWT group were comparable to the outcomes previously reported after intramedullary screw fixation alone.2,10 Therefore, the observed differences between the groups may reflect relatively slower recovery in the Non-ESWT group rather than solely an effect of F-ESWT. Furthermore, although the differences in bone union and return to sport were statistically significant, the clinical significance of these relatively modest differences remains uncertain. Nevertheless, even a modest reduction in recovery time may be relevant for high-level athletes.
This study has several limitations. First, this was a retrospective study, and the indication for F-ESWT was determined based on patient preference. The specific reasons why individual patients declined F-ESWT were not reliably determined. Therefore, unmeasured factors influencing treatment choice, including patient motivation and practical considerations, may have differed between the groups and introduced substantial selection bias. In addition, although the scheduled clinical and radiographic follow-up protocol was identical between the groups, patients in the ESWT group had more frequent clinical contact with the medical team than those in the Non-ESWT group. Thus, a potential Hawthorne effect related to increased clinical contact cannot be excluded and may have influenced rehabilitation behavior or return-to-sport timing. Second, the sample size was small, and an a priori sample size calculation was not performed. The post-hoc power was .567, indicating limited statistical power, and post-hoc power analysis does not substitute for an a priori sample size calculation. Therefore, adequately powered prospective studies are needed to confirm these findings. Although the distribution of Torg classification did not differ significantly between the groups, the small number of patients within each Torg category precluded a meaningful stratified analysis. Therefore, whether the effect of F-ESWT differs according to Torg classification remains unclear. In addition, although most patients were soccer players and the distribution of sports did not differ significantly between the groups, sport-specific physical demands may have influenced the timing of return to sport. Third, the study population included patients with both zone 2 and zone 3 fractures. Although the subgroup analysis revealed no significant differences in the clinical outcomes between zone 2 and zone 3 fractures within each group, the small sample size may have limited the statistical power to detect meaningful differences. Therefore, the absence of significant differences should not be interpreted as evidence of equivalence between these fracture locations. Fourth, the follow-up period was relatively short (minimum of 2 years), although previous studies have demonstrated that the majority of refractures occur within 2 years after intramedullary screw fixation.7 Fifth, bone union in the primary analysis was assessed by a single non-blinded orthopaedic surgeon using plain radiographs, with CT used only when radiographic findings were inconclusive. Although an additional blinded assessment by two independent observers demonstrated excellent interobserver reliability, observer bias in the original assessment cannot be completely excluded. Furthermore, because bone union was assessed at approximately 2-week intervals, the exact timing of bone union could not be determined. This limitation should be considered when interpreting the relatively modest difference in time to bone union between the groups. Sixth, return to the original sport was defined as participation in at least one game at the pre-injury level. Therefore, this outcome may not necessarily reflect full functional recovery. Finally, all surgical procedures, perioperative management, and the primary clinical and radiological evaluations were performed by a single orthopaedic surgeon, which may limit the generalizability of our findings.
5. Conclusion
The application of F-ESWT after intramedullary screw fixation for Jones fractures may be associated with earlier bone union and return to the original sport in high-level athletes. Further prospective studies with larger sample sizes, particularly randomized controlled trials, are needed to validate these preliminary findings.
Ethics declaration
The authors have NOT obtained informed consent from participants or their legal representatives. Written informed consent was not obtained because of the retrospective nature of the study. Information regarding the study was disclosed on the institutional website, and participants were provided with the opportunity to opt out of the study. This opt-out consent procedure was approved by the institutional review board.
This study was performed in compliance with relevant laws, regulatory frameworks and guidelines where the research took place. This study was conducted in accordance with Declaration of Helsinki. This study was approved by the Ethics Review Board of Hyogo Medical University. (Approval No. 4932)
Data availability statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.
Funding/support statement
The authors received no financial support for the research, authorship and publication of this report.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
The authors thank Mr. Nicholas Pollifrone for assistance in English editing the manuscript.
Footnotes
Supplementary data to this article can be found online at https://doi.org/10.1016/j.asmart.2026.09.001.
Contributor Information
Shota Morimoto, Email: 14hmfc@hyo-med.ac.jp.
Shinichi Yoshiya, Email: yoshiya0307@gmail.com.
Takatoshi Morooka, Email: morooka0818@gmail.com.
Masashi Nakamura, Email: ph.so.masa@gmail.com.
Yuta Matsumae, Email: yuball0306@gmail.com.
Toshiya Tachibana, Email: tachi@hyo-med.ac.jp.
Tomoya Iseki, Email: tomoyai0119@gmail.com.
Appendix A. Supplementary data
The following is the Supplementary data to this article:
References
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Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.