Explanation for the choice of comparators

The absence of prospective studies on weight bearing protocols prevents the favoring of one rehabilitation regimen (PWB or RWB) over the other in the treatment of surgically managed trauma patients with DIACFs. Consequently, there is a clear need for a large-scale prospective, high-quality RCT to evaluate whether the PWB protocol yields improved functional outcomes, radiographical parameters, enhanced quality of life, and reduced costs. Such a trial should also examine cost-effectiveness and complications, as cost considerations could be pivotal in decision-making, particularly when both rehabilitation regimens yield comparable PROMs.

Intervention description Permissive weight bearing

The PWB protocol represents a relatively new approach to early weight bearing, enabling earlier postoperative weight bearing. Progression of weight bearing is determined by the patient’s subjective experience, such as pain levels and weight bearing tolerance, along with the clinical expertise of the treating physician and physiotherapist, in line with the PROMETHEUS protocol [12]. The rehabilitation regimen commences with 2 weeks of immobilization to facilitate wound healing. Subsequently, patients are allowed to bear as much weight as tolerated, guided by their pain levels and comfort [12].

Restrictive weight bearing

The RWB protocol adheres of 8 to 12 weeks of postoperative weight bearing restriction, in the range of 0–10%, so-called touching load, as outlined in the current AO Guidelines [16]. Following this initial phase, which entails restricted weight bearing, a gradual increase in weight bearing is implemented. This entails a weekly increment of 25% over the course of 4 weeks. During each patient-physician encounter, the weight bearing advice provided to the patient is meticulously recorded. This includes whether the recommendation is for unloaded, partial weight bearing with clarification, or full weight bearing. Furthermore, any additional advice imparted to the patient is also documented.

Criteria for discontinuing or modifying allocated interventions

In accordance with Sect. 10, subsection 4 of the WMO, the sponsor will suspend the study if there is sufficient reason to assume that continuing the study would compromise the health or safety of the subjects. The sponsor will promptly notify the accredited Medical Ethical Board of any temporary suspension, providing the reasons for such action without undue delay. The study will remain suspended until a further (positive) review from the accredited Medical Ethical Board is obtained. Throughout this process, the Coordinating Investigator (CI) will ensure continuous communication with the enrolled subjects.

Besides, the LI or CI reserves the right to withdraw a participant from the study due to urgent medical reasons. Participants retain the autonomy to withdraw from the study at any point for any reason, without facing any repercussions. Data collected up until the time of withdrawal will be utilized for study purposes.

Strategies to improve adherence to interventions

This is not applicable to our study, as strategies to improve adherence to intervention protocols and procedures for monitoring adherence are not required.

Relevant concomitant care permitted or prohibited during the trial

There are no relevant restrictions on concomitant care or interventions during this study. All standard concomitant care is permitted.

Provisions for post-trial care

The sponsor maintains liability insurance in accordance with article 7 of the Medical Research Involving Human Subjects Act (WMO). Aftertreatment following the PWB protocol is already implemented in several hospitals in the Netherlands, including for DIACFs. While no adverse effects have been noted from clinical experience, there may be potential risks that are currently unknown. Additionally, a recent retrospective study, not yet published, and a systematic review and meta-analysis reported no negative effects on patients’ reported quality of life, pain, or complication rates.

Outcomes Primary outcome

The primary outcome is the functional outcome score, defined by the American Orthopaedic Foot & Ankle Society (AOFAS). The AOFAS score is a clinician-based assessment tool that integrates both subjective and objective information. Patients provide self-reports on their pain levels, while physicians evaluate alignment. This scoring system is intended to assist physicians in standardizing patient assessments, thereby facilitating the comparison of study results with previous data. Scores on the AOFAS scale range from 0 to 100, with a score of 100 points indicating optimal health for the foot and ankle [21]. Time points: measured at 2 weeks, 6 weeks, 12 weeks, and 6 months post-surgery.

Secondary outcomes

Secondary outcomes encompass several measures.

1.

The Maryland Foot Score (MFS): The MFS is a tool for assessing foot disorders, comprising evaluations of pain, gait, functional activities, and cosmesis. Scores range from 0 to 100 points, with < 50 indicating poor, 50–74 as fair, 75–89 as good, and 90–100 as excellent outcomes [22]. Time points: collected at 2 weeks, 6 weeks, 12 weeks, and 6 months post-surgery.

2.

Health-related quality of life (HRQoL) using the EuroQoL 5-Dimension 5-Level (EQ-5D-5L): This self-administered questionnaire comprises five dimensions (mobility, self-care, daily activities, pain/discomfort, and depression/anxiety), each rated on five levels. Utilities calculated using preferences from the Dutch tariff will enable Quality Adjusted Life Years (QALY) scoring, besides the questionnaire is recommended by the Dutch guidelines [23, 24]. Time points: collected at baseline, 2 weeks, 6 weeks, 12 weeks, and 6 months post-surgery.

3.

Radiographical characteristics: Evaluation of Böhlers angle and posterior facet joint alignment via radiographic assessment by a blinded radiologist will be conducted at scheduled physician visits. CT scans early post-operatively and at 6 months will be used to measure differences in Böhlers angle and posterior joint alignment [25]. Differences in the Böhlers angle and posterior joint alignment (Δ = CT6months—CTpost-op.) will be calculated. Normal Böhlers angle ranges between 25° and 40° [26]. Intra-articular step-off or gap < 2 mm of the posterior facet is considered well-reduced [3]. Time points: early post-operative (‘baseline’) and at 6 months post-surgery CT scan.

4.

Medical consumption and productivity: Measured using the Medical Consumption Questionnaire (iMCQ) and Productivity Costs Questionnaire (iPCQ). The iMCQ assess healthcare utilization, while the iPCQ captures productivity losses. The iPCQ and iMCQ are generic and complimentary questionnaires, that can be used in every indication and are adapted to the context of this study [27]. Time points: collected at baseline, 12 weeks, and 6 months post-surgery.

5.

Total complication rate: A wound infection is defined as (but not limited to) purulent wound drainage, inflammation, erythema, fever, increased white blood cell count, increased C-reactive protein and/or increased erythrocyte sedimentation rate, necessitating admission for antibiotic treatment and/or revision surgery for infection.

A dislocation is defined as the migration of fracture parts, defined as >3 mm articular step-off or gap and/or varus/valgus malalignment > 5° after weight bearing. A non-union is defined as no radiographic union achieved after 6 months or no progress in healing. Failure of osteosynthesis is defined as loosening or breakage of implants, including the rate of reoperation (e.g., leading to removal of material, arthrodesis). Postoperative arthritis will be screened on CT scans. Time points: evaluated at 2 weeks, 6 weeks, 12 weeks, and 6 months post-surgery.

Participant timeline

Regular follow-up will be performed for both weight bearing regimes. Appointments will be scheduled at 0, 2, 6, and 12 weeks, and at 6 months (Fig. 2).

Fig. 2

Overview of the measurements

Sample size

To our knowledge, there is no literature available that directly compared our primary outcome (AOFAS Score) in PWB versus RWB for surgically treated patients with DIACFs. Therefore, unfortunately, the MCID is unknown for the AOFAS Score [28, 29].

However, the estimated minimal clinical difference (MCID) can be calculated as one half of the standard deviation (0.5 SD) [30]. Preliminary results of a systematic review that is currently performed by our group, found a mean AOFAS Score of 83.7 (SD 8.5) for the RWB group. 0.5 × 8.5 results in a MCID of 4.3, respectively.

Besides, a recent Cochrane review reported a MCID for the AOFAS Score in other foot conditions that range from 2.0 to 7.9 [29]. This results in a mean MCID of (2.0 + 7.9)/2 = 5, respectively.

For this sample size calculation, a MCID of 5 points was assumed, approximating a 0.5 SD of the estimated mean AOFAS score after RWB for surgically treated patients with DIACFs [30].

In order to be able to detect such a difference between the two groups, assuming that an equal number of patients in both groups will be included, with an alpha of 5% and beta of 20% (power 80%), a pooled SD of 8.5 and a true difference of zero points between the RWB and PWB group the sample size should be at least 46 for both groups = 92 in total. Anticipating a 20% drop out a total of 115 patients must be recruited for this study. The sample size calculation was performed with a two-sample mean test for non-inferiority using the TrialSize package within “R.”

Recruitment

Each medical institution participating in “the PIONEER study” will appoint a Local Investigator (LI). The Coordinating Investigator (CI) will oversee the trial and provide guidance to all LIs across each medical institution. Together, the LIs (comprising trauma or orthopedic surgeons) and the CI will constitute “the PIONEER study” group. The LIs will actively screen patients for eligibility at their institution’s emergency department or outpatient clinic. In cases where there is uncertainty regarding the eligibility criteria, the LI will communicate with the CI, who will make the final decision.