Non-tourniquet strategy with high-position low-perfusion in distal humeral fracture surgery: reduces swelling without increasing blood loss

Abstract

Introduction

To evaluate the feasibility of non-tourniquet strategy combined with “High-position Low-Perfusion” positioning in distal humeral fractures ORIF (DHF-ORIF), and to investigate its effects on perioperative blood loss, postoperative rehabilitation, and functional outcomes.

Methods

Prospective inclusion of patients aged 18–45 with distal humeral fractures, randomly divided into an experimental group without tourniquets (Group A) and a control group with traditional tourniquets (Group B). The Group A adopted a lateral position with high and low perfusion of the affected limb, and received intravenous injection of TXA (15 mg/kg) combined with continuous flushing with 4 ℃ physiological saline during the operation; The control group received routine use of tourniquets. Primary Outcomes: perioperative blood loss, elbow ROM and degree of limb swelling. Secondary Outcomes: Postoperative VAS score, Mayo elbow joint score and DASH score, and incidence of complications.

Results

No significant difference was observed in total perioperative blood loss between the Group A and the Group B (240.78 mL vs. 228.53 mL, p > 0.05). However, the Group A demonstrated significantly reduced postoperative drainage volume and hidden blood loss (p < 0.05). The Group A exhibited significantly superior outcomes in terms of VAS scores and limb swelling, compared with the control group. Additionally, elbow ROM improvement was more significant at 2–4 weeks and 2 months postoperatively in the Group A. At the 6-month follow-up, the Group A showed significantly higher Mayo scores (89.78 ± 11.89 vs. 83.55 ± 16.29) compared with the control group (p = 0.036). Furthermore, the Group A had significantly lower wound complication rates and shorter hospital stays (7.25 ± 1.53 vs. 8.11 ± 2.34 days, p = 0.037).

Conclusion

The non-tourniquet strategy combined with “High-position Low-Perfusion” positioning is safe and effective for DHF-ORIF. It effectively controls postoperative swelling and pain without increasing perioperative blood loss, leading to improved clinical outcomes and quality of life.

Introduction

Since Harvey Cushing first introduced pneumatic tourniquets into limb orthopedic surgery in 1904, they have played a crucial role in such procedures [1, 2]. The introduction of pneumatic tourniquet aims to maintain a relatively bloodless field during extremity surgery, minimize blood loss, aid identification of vital structures, and expedite the procedure. However, with the widespread use of tourniquets, surgeons have realized that this is not a perfect solution as they may induce ischemia-reperfusion injury, delayed muscle strength recovery, compressive nerve loss, potentially infected wound hematoma, vascular injury, tissue necrosis, and compartment syndrome, among other adverse outcomes [3, 4].

Following the success of wide-awake local anaesthesia without tourniquet (WALANT) in hand surgery [5], an increasing number of centres have abandoned tourniquet use during total knee arthroplasty (TKA) without increasing peri-operative blood loss while maintaining favourable clinical outcomes [6–8]. A meta-analysis suggests that although intraoperative tourniquet usage in cases of ankle ORIF results in significant reductions in duration of surgery, this may be at the expense of higher patient-reported pain scores and reduced range of motion postoperatively [9]. Complex distal humeral fractures (AO/OTA C2–C3) are notoriously challenging to manage. In our clinical impression suggests that routine use of a pneumatic tourniquet exacerbates post-operative myalgia and swelling formation, thereby diminishing early elbow range of motion and exerting a protracted, adverse effect on both functional recovery and patient-reported physical and mental health.

We hypothesize that distal humeral fracture open reduction and internal fixation (DHF-ORIF) performed without a pneumatic tourniquet will yield superior functional outcomes and improved quality of life without a clinically relevant increase in peri-operative blood loss.

Materials and methods

A single-surgeon group, randomized, patient- and assessor-blinded (physiotherapist) controlled trial was performed between March 2023 and January 2025. Participants were allocated to either the tourniquet or non-tourniquet group using a computer-generated random number table. All postoperative outcome measurements were performed by three independent physical therapists who were blinded to the group assignments. The research was carried out in accordance with the Declaration of Helsinki’s guiding principles and received approval from the hospital ethics committee (No. 202303003). All participants gave their permission in writing after being fully informed. This prospective randomized controlled study is a sub-study of a upper limb fractures project initially registered in the Chinese Clinical Trial Registry (28/12/2017, ChiCTR-INC-17014197) and conducted in accordance with the Consolidated Standards of Reporting Trials (CONSORT) statement.

Patients

Recruited patients were aged 18–45 years, presented with DHFs and were scheduled for ORIF. Exclusion criteria were: (1) contraindication or allergy to tranexamic acid (TXA); (2) injury-to-surgery interval > 3 weeks; (3) prior elbow fracture, post-traumatic arthritis, rheumatoid arthritis, or osteoarthritis; (4) multiple trauma, open fracture, or concomitant neurovascular injury; (5) BMI > 30 kg/ m² or abnormal muscle mass (e.g., competitive athletes); and (6) incomplete outpatient follow-up data. Furthermore, after randomization but prior to the induction of anesthesia, the surgeon may exclude any patient from the trial for medical reasons; this decision is at the surgeon sole discretion.

Surgical technique, material selection and perioperative management

Prior to 2023, tourniquet application was standard practice for all distal humeral fracture open reduction and internal fixation (DHF-ORIF) procedures in our centre. Consequently, before trial initiation, the surgical team—comprising one senior orthopedic surgeon and two assistants—completed a structured training program focused on tourniquet-free ORIF techniques. Electrocautery was used strictly based on the presence of active bleeding vessels during the procedure, regardless of tourniquet use.

The tourniquet group underwent surgery with a tourniquet (24 inches, single-bladder, dual-port, Zimmer) applied 2–5 cm proximal to the axilla at a pressure of 200 mmHg and the other group underwent surgery without a tourniquet. All patients received general anesthesia under light-to-moderate sedation, combined with a brachial plexus block for intraoperative anesthetic supplementation and postoperative analgesia. Patients were positioned in the lateral decubitus orientation. The ulnar nerve was routinely exposed and decompressed. Intraoperatively, the primary surgeon individualized the decision to perform an olecranon V-shaped osteotomy based on the specific fracture configuration. Following evacuation of the hematoma and debris, the articular surface was fixed with Kirschner wires (K-wires) or lag screws. Subsequently, internal fixation of the medial and lateral columns of the distal humerus was performed using an anatomical locking compression plate (LCP). A single closed-suction drain was placed in the surgical site postoperatively.

In the combined non-tourniquet protocol (CNTP) cohort, patients were positioned in the lateral decubitus orientation. The surgery was performed via the posterior midline elbow approach in the standard lateral decubitus position, with the affected limb was elevated using a padded arm holder to approximately 30–40 cm above the heart, forming a 90-degree angle with the horizontal plane (Fig. 1). The surgical field was continuously irrigated with 4 °C saline throughout the procedure. Intravenous tranexamic acid (TXA, 15 mg/Kg) was administered 10 min prior to incision. Prophylactic cefuroxime sodium (1.5 g IV) was administered preoperatively and twice postoperatively; Mannitol (125 mL IV) was administered twice daily during the perioperative period. The postoperative regimen included scheduled celecoxib (200 mg orally twice daily), topical cryotherapy (ice pack application), and oral oxycodone (5 mg) administered as needed for breakthrough pain. Postoperative day 1, the patient underwent rehabilitation training under the supervision of a physiotherapist, including active assistance, active range of motion exercises, and reinforcement exercises until discharge followed. A home-based exercise program followed.

Fig. 1.

The patient is placed in the lateral decubitus position, with the affected upper limb elevated approximately 30–40 cm above the cardiac level using a padded arm rest to reduce perfusion pressure without using a tourniquet

Data collection

The primary outcome measures were perioperative blood loss (PBL), Hb decrease, postoperative swelling, and active flexion of the elbow joint.

• The calculation of PBL was based on the classic Nalder [10] and Gross [11] equations, which have been used in our previous studies. The specific calculation steps are as follows:

PBV (L) = K₁ × h³ + K₂ × w + K₃ [h: height (m), w: weight (kg)];

male patients K₁ = 0.366 9, K₂ = 0.032 19, K₃ = 0.604 1;

female patients K₁ = 0.356 1, K₂ = 0.033 08, K₃ = 0.183 319.

PBL(mL) = PBV×(Hct₁- Hct₂)+Hb_trans.

Hct₁ is the first routine blood test after the patient admitted to the hospital; Hct₂ is the lowest postoperative value obtained by routine blood tests.

• Bilateral elbow circumference was measured to assess swelling. Measurements were taken with a measuring tape at a standardized point 10 cm proximal to the antecubital crease while patients were positioned supine. The difference between the affected and unaffected sides was used to quantify the degree of swelling. Measurements were recorded preoperatively and postoperatively on days 3, 7, 14, and 30.

• Active elbow flexion and extension were measured using a standard plastic goniometer with 1° increment markings and 30 cm arms. Patients were positioned supine on an examination table during measurements. Outcome measurements were collected at 2 weeks, 4 weeks, and 2 months postoperatively. All measurements were performed by three independent physical therapists from our institution. To enhance measurement reliability, the physical therapists underwent standardized training prior to study initiation and throughout the data collection period.

Secondary outcomes included perioperative pain scores, upper extremity deep venous thrombosis (UEDVT), wound complications, and short-term clinical outcomes.

• Perioperative pain was assessed using a Visual Analog Scale (VAS). Measurements were obtained preoperatively, and on postoperative day (POD) #1, POD#3, POD#5, POD#14, and POD#30. All assessments were conducted prior to rehabilitation sessions, with patients at rest and without administration of additional analgesic agents.

• Postoperative duplex ultrasonography was routinely performed. Patients with UEDVT received oral Rivaroxaban (10 mg twice daily), with unrestricted active and passive elbow joint movement permitted.

• Functional outcomes and quality of life were evaluated by physical therapists at 6-month follow-ups using: (1) the Mayo Elbow Performance Score (MEPS) for elbow-specific function, and (2) the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire for upper extremity disability.

Sample-size calculations

We assumed that this CNTP application increases intraoperative blood loss (IBL) more than 50% compared with control group. Setting the pre-study power of test (β) as 0.9, significant difference (α) as 0.05, and standard effect size of 0.65 indicated that 30 patients were required for each group. To compensate for the expected dropouts (10%), 33 patients per group were planned to include in this study.

Statistical analysis

SPSS version 22.0 was used for all statistical analyses (IBM Corp., Armonk, NY, USA). To compare continuous factors, Mann-Whitney U or t-tests were used to show continuous variables as mean± standard deviation (SD). Comparisons were made using the Chi-square or Fisher’s exact test, as applicable, and discrete variables were shown as frequencies with percentages. P values < 0.05 were considered to be statistically significant.

Results

Patient clinical and demographic information

A total of 71 participants were enrolled in this study, with the selection process detailed in the CONSORT flow diagram (Fig. 2). The cohort had a mean age of 38.11 ± 7.17 years (range: 22–45 years), comprising 37 males (52.11%) and 34 females (47.89%). The mean BMI was 25.34 ± 4.47 kg/m². Comorbidities were present in 12 patients (16.90%). According to the AO/OTA classification system, 39 fractures (54.93%) were classified as type 13-C2 and 32 (45.07%) as type 13-C3 (Details in Table 1).

Fig. 2.

CONSORT flow diagram of patients eligible for this study

Table 1.

Preoperative patient characteristics and surgery-related characteristics

Varibles	CNTP group	Control group	P-value
Gender
Female	19	15	0.128
Male	14	23
Age (years)	37.78 ± 6.73	38.41 ± 7.35	0.354
BMI (kg/m2)	26.80 ± 4.47	26.12 ± 5.54	0.285
Smoke	7	11	0.455
Alcoholism	3	2	0.530
Injury mechanism
High energy	13	19	0.370
Low energy	20	19
Medical morbidity
Hypertension	2	1	0.474
Diabetes	1	2	0.641
Chronic heart disease	0	1	0.348
Chronic respiratory disease	1	0	0.280
Liver disease	1	1	0.919
Renal disease	0	1	0.348
Comorbidities number
0	28	33	0.810
1–2	5	5
AO/OTA
13-C2	17	22	0.590
13-C3	16	16
Hb (g/L)	127.22 ± 10.32	126.71 ± 8.52	0.411
Olecranon Osteotomy	7	9	0.804
Duration of surgery	110.55 ± 25.71	106.51 ± 17.17	0.223
Duration of the bloodless field(min)	-	57.29 ± 15.45	-

Abbreviations: BMI, Body mass index; Hb, Hemoglobin; CNTP, combined non-tourniquet protocol

Primary outcomes

The CNTP group use did not significantly increase perioperative blood loss or reduce Hb levels (P > 0.05) (Details in Table 2; Fig. 3). All patients developed swelling by postoperative day 1 (POD#1), but the CNTP group showed significantly accelerated resolution from POD#3 onward (Fig. 4). Moreover, the CNTP group achieved significantly greater elbow range of motion (ROM) at 2 weeks, 4 weeks, and 2 months postoperatively.

Table 2.

The primary outcomes

	CNTP group	Control group	P-value
Hb (g/L)
POD#1	121.55 ± 8.16	122.73 ± 7.71	0.266
POD#3	120.64 ± 5.51	122.14 ± 6.09	0.141
Hb drop (g/L)	6.14 ± 2.21	6.05 ± 1.12	0.413
Elbow ROM
2 weeks
Flexion	105.11°±17.54°	90.37°±24.45°	< 0.001
Extension	30.60°±17.41°	44.44°±21.17°	0.002
Pronation	44.73°±16.52°	40.98°±17.41°	0.207
Supination	50.53°±14.49°	47.93°±16.77°	0.245
4 weeks
Flexion	110.27°±22.53°	104.23°±27.67°	0.160
Extension	24.14°±16.91°	38.11°±25.85°	0.008
Pronation	48.42°±11.87°	46.14°±16.75°	0.258
Supination	55.54°±7.27°	50.15°±13.73°	0.024
2 months
Flexion	120.54°±15.73°	110.10°±18.22°	0.006
Extension	17.84°±15.35°	26.47°±18.46°	0.018
Pronation	68.50°±15.63°	57.97°±13.27°	0.001
Supination	72.55°±15.40°	67.91°±19.74°	0.139

Abbreviations: PBL, perioperative blood loss; ROM, range of motion; POD#1, the first postoperative day; POD#3, the third postoperative day

Note: Elbow ROM was measured under resting conditions without prior administration of oral analgesic medication

Fig. 3.

Comparison of perioperative blood loss between the CNPT and control groups. Abbreviations: PBL, perioperative blood loss; IBL, Intraoperative blood loss; HBL, Hidden blood loss; DV, Drainage volume

Fig. 4.

Perioperative arm circumference and swelling of the affected limb. Note: Swelling severity was stratified by arm circumference difference: mild (1–3 cm), moderate (3–5 cm), and severe (> 5 cm) compared to the contralateral limb

Secondary outcomes

Patients in the CTNP group demonstrated significantly lower early postoperative pain scores compared to the tourniquet group, with a progressive decline observed over the initial follow-up period. Wound complications were significantly more prevalent in the tourniquet group (6.06% vs. 13.16%, p < 0.05), with blister formation being the predominant adverse event (n = 3, 4.23%). Furthermore, one patient in the tourniquet group developed confirmed UEDVT postoperatively. At the 6-month outpatient follow-up, analysis of standardized questionnaires revealed that the tourniquet-free group achieved significantly superior clinical outcomes and quality of life scores compared to the control group (Details in Table 3).

Table 3.

The secondary outcomes

	CNTP	Tourniquet	P-value
VAS
Preoperative	4.44 ± 1.49	4.51 ± 1.77	0.429 0.256 0.099
POD#1	5.43 ± 2.01	5.77 ± 2.31
POD#3	4.88 ± 1.79	5.41 ± 1.65
POD#7	4.57 ± 2.18	4.86 ± 1.78	0.269
POD#14	4.43 ± 2.21	4.61 ± 1.51	0.343
POD#30	3.13 ± 1.78	3.57 ± 1.88	0.316
Wound complications			0.317
Blister	1	3	0.375
Dehiscence	0	1	0.348
Hematoma	1	1	0.919
Edgenecrosis	0	0	-
Superficial infection	0	0	-
UEDVT*	0	1	0.348
MEP Score
Pain	39.63 ± 10.14	35.77 ± 14.48	0.102
Motion	19.34 ± 1.17	16.16 ± 4.77	< 0.001
Stability	10.00 ± 0.00	10.00 ± 0.00	-
Function	22.61 ± 2.74	18.78 ± 7.24	0.002
Total	89.78 ± 11.89	83.55 ± 16.29	0.036
DASH scores	15.88 ± 10.51	20.79 ± 17.77	0.084
Length of stay	7.25 ± 1.53	8.11 ± 2.34	0.037

Abbreviations: VAS, Visual analog scale score MEP; UEDVT, Upper extremity deep venous thrombosis; Mayo elbow performance, DASH: Disabilities of the Arm, Shoulder and Hand

Postoperative upper limb duplex ultrasound examination showed the presence of brachial vein thrombosis. Our Vascular Medicine department recommends starting anticoagulation therapy was initiated with enoxaparin 40 mg subcutaneously once daily for two days followed by rivaroxaban 15 mg twice daily for 21 days. Postoperative rehabilitation program with early passive range of motion followed by gradual transition to active range of motion and strength training with physical therapy There were no recurrent thromboembolic events or any complications of anticoagulant therapy observed during the 30 day postoperative follow-up.

Fig. 5.

A representative case of a 28-year-old female who underwent ORIF for an AO/OTA 13-C3 distal humeral fracture, who chose conservative treatment for her distal radius fracture. The surgery was performed using a non-tourniquet strategy combined with “High-position Low-Perfusion” positioning and a dual-modality hemostatic protocol (intravenous TXA and low-temperature saline irrigation). Postoperatively, the patient received remote rehabilitation guidance and performed family-supervised exercises for the affected limb (a), achieving satisfactory clinical outcomes at the 2-week (b), 4-week (c), and 2-month (d) follow-up. The patient initiated active and passive functional exercises on postoperative day 1, with swelling markedly reduced by day 5 (e)

Discussion

The primary finding of this study is that abandoning traditional tourniquet use during distal humeral fracture (DHF) surgery did not increase perioperative blood loss. The tourniquet-free strategy demonstrated significant advantages in early postoperative pain control and limb swelling management, factors directly related to patient comfort and the initiation of early rehabilitation. Furthermore, this approach yielded satisfactory clinical outcomes and functional scores.

Traditional orthopedic practice has long advocated the use of tourniquets in limb surgery, mainly based on their established efficacy in reducing intraoperative blood loss and optimizing the surgical area [12]. Supporters argue that the bloodless surgical field created by tourniquets can promote precise anatomical reduction of fractures and precise placement of prostheses/implants, theoretically reducing blood loss and shortening surgical time [13, 14]. However, these conclusions mainly stem from surgeon-centered clinical studies, whose core limitations lie in the systematic neglect of tourniquet related complications (such as nerve damage, compartment syndrome, thromboembolic events) and patient subjective experiences (such as increased postoperative pain, limb numbness).It is worth noting that these overlooked complications and patient perceptions are key factors affecting long-term clinical outcomes, including delayed functional recovery, prolonged hospitalization, and decreased patient satisfaction [15, 16].

In this study, the group without tourniquet received intravenous infusion of TXA during surgery and continuous irrigation of the surgical field with cold saline (4 °C). The perioperative and blood loss was comparable to that of the tourniquet group (240.78 vs. 228.53 mL; P > 0.05).Notably, postoperative drainage and hidden blood loss were significantly lower in the non-tourniquet group than in the tourniquet group. Additionally, patients in the non-tourniquet group experienced milder limb swelling. These data indirectly suggest that the CNTP strategy offers significant advantages in mitigating postoperative soft tissue ischemia-reperfusion injury, a finding also reported by Xie et al. in a total knee arthroplasty (TKA) meta-analysis of randomized controlled [17].

In clinical practice, the first two weeks post-surgery are considered a critical window for functional exercise after DHF-ORIF, and early elbow range of motion (ROM) is a key predictor of clinical outcomes [18–20]. These findings suggest that effective control of pain and swelling not only improves perioperative comfort but also reduces patient apprehension toward postoperative rehabilitation, which is crucial for facilitating early active and passive functional exercises. At the 6-month follow-up, patients in the CNTP group demonstrated superior functional and satisfaction. In the study cohort (aged 18–45 years), patients demonstrated significantly greater needs for functional independence and social participation compared to older populations, and most younger patients are in critical career development phases, delayed postoperative functional recovery directly disrupts employment continuity [21, 22]. Furthermore, limited social activities and perceived disability significantly increase the risk of anxiety and depression, posing a significant adverse impact on patients’ physical and psychological recovery [23–25]. These outcomes have been systematically overlooked in previous surgeon centered studies, but they are precisely the primary criteria for evaluating surgical success in middle-aged and young patients.

To address the potential negative impact of tourniquets, researchers have proposed a series of exploratory studies such as personalized inflation pressure protocols [26], intermittent tourniquet application [27], intraoperative silicone tourniquets [28], and prophylactic oral melatonin administration [29] et al., but their actual clinical effects remains to be definitively established. The Wide-Awake Local Anesthesia No Tourniquet (WALANT) technique has gained widespread adoption in contemporary orthopedic practice and has been successfully applied to ORIF of olecranon [30], distal radius [31], clavicle [32], ankle fractures [33]. It is considered an excellent alternative to local tourniquet, with or without sedation or general anesthesia, and can achieve satisfactory comfort without increasing hospitalization costs [34]. However, applying tourniquet-free techniques to distal humerus ORIF presents formidable challenges, primarily due to the complex three-dimensional anatomy of the elbow and the demanding requirements for surgical exposure. While this approach aligns with the core principles of WALANT—mitigating tourniquet-induced pain and swelling, and facilitating early rehabilitation—its adoption in mainstream practice remains limited.

Despite these challenges, our study still highlights several innovative aspects recommending. First, all patients were positioned in the lateral decubitus position, with the affected limb maintained in a “High-position Low-Perfusion” state. Second, a dual-modality hemostatic protocol was implemented: intravenous TXA (15 mg/kg) combined with topical irrigation using 4 °C cold saline to minimize intraoperative bleeding. Third, we leveraged an Internet-based hospital platform to facilitate seamless interdisciplinary communication among surgeons, therapists, and patients, enabling the delivery of individualized rehabilitation protocols and real-time guidance on functional exercises.

This study has several limitations. First, its single-center, small sample size may limit the generalizability of our findings. Second, the tourniquet-free technique has a learning curve; potential improvements in surgical proficiency throughout the study period could have introduced performance bias. Third, the control group exclusively consisted of patients undergoing general anesthesia with a tourniquet. Consequently, further studies are warranted to evaluate the efficacy of the tourniquet-free strategy when combined with regional or local anesthesia. Fourth, in surgeries performed without a tourniquet, surgeons may have used more meticulous hemostasis and increased cautery application, whereas in the tourniquet group, this aspect may not have been equally emphasized. This difference in intraoperative hemostasis behavior could potentially influence the outcomes and represents an inherent performance bias in such non-blinded surgical trials. Fifth, the non-tourniquet group includes multiple simultaneous interventions, include absence of tourniquet, TXA administration, cold saline irrigation, and limb elevation. The observed results cannot be specifically attributed solely to the absence of a tourniquet, but rather to the CNTP. Finally, we did not analyze inflammatory markers (e.g., WBC, NEUT%, CRP, IL-6), which will be a focus of our future investigations.

Conclusion

The strategy of non- tourniquet uses a “High position-Low perfusion” and TXA + low-temperature saline dual-mode hemostasis to ensure perioperative hemostasis while significantly reducing postoperative pain, swelling, accelerating elbow joint function recovery, and improving patients’ quality of life. This technology avoids the risk of complications related to tourniquets, meets the core needs of middle-aged and young patients for functional independence and early return to society.

Abbreviations

VAS

Visual analog scale

PBL

Perioperative blood loss

BMI

Body mass index

DASH

Disabilities of the Arm, Shoulder and Hand

ROM

Range of motion

TXA

Tranexamic acid

Author contributions

Conceptualization: KZ, QW and ML; Data curation: ZW, XA, TR, QW and HX; Formal analysis: ZW and XA; Roles/Writing-original draft: ZW, ZL and BW.All authors reviewed the manuscript.

Funding

No funding was received for the project.

Data availability

Data is available on reasonable request via contacting the corresponding authors (Ming Li or Qian Wang).

Declarations

Ethics approval and consent to participate

This study was conducted in accordance with the Declaration of Helsinki. The protocol was approved by the Xi’an Honghui hospital Ethics Committee, reference number 202303003. All participants provided written informed consent to participate. They were informed about the study’s purpose, procedures, potential risks, and benefits. Participants were assured that participation was voluntary and that they could withdraw at any time without any consequences. All images have been completely anonymized through cropping and composition to prevent identification of any individual.

Competing interests

The authors declare no competing interests.