Anti-TNF (adalimumab) injection for the treatment of adults with frozen shoulder during the pain predominant stage protocol for a multi-centre, randomised, double blind, parallel group, feasibility trial

Objectives The Anti-Freaze-F trial will assess the feasibility of conducting a large randomised controlled trial to assess whether intra-articular injection of anti-TNF (adalimumab) can reduce pain and improve function in people with pain predominant early stage frozen shoulder. Methods and analysis We are conducting a multi-centre, randomised feasibility study, with an embedded qualitative sub-study. We will recruit adults ≥18 years with a new episode of shoulder pain attributable to early stage frozen shoulder, recruited from at least five UK NHS musculoskeletal and related physiotherapy services. Participants (n=84) will be randomised (centralised computer generated 1:1 allocation) to receive either: 1) intra-articular injection of anti-TNF (adalimumab 160mg) or 2) placebo injection (saline [0.9% sodium chloride]), both under ultrasound guidance. A second injection of the allocated treatment (adalimumab 80mg) or equivalent volume of placebo will be administered 2–3 weeks later. All participants will receive a physiotherapy advice leaflet providing education and advice about frozen shoulder and pain management. The primary feasibility objectives are: 1) the ability to screen and identify potential participants with pain predominant early stage frozen shoulder; 2) willingness of eligible participants to consent and be randomised to intervention; 3) practicalities of delivering the intervention, including time to first injection and number of participants receiving second injection; 4) standard deviation of the Shoulder Pain and Disability Index (SPADI) score and attrition rate at 3 months (i.e. 12 weeks) post-randomisation in order to estimate the sample size for a definitive trial. We will also assess follow up rates and viability of patient-reported outcome measures and range of shoulder motion for a definitive trial. Research Ethics Committee approval (REC 21/NE/0214). Trial registration number ISRCTN 27075727; EudraCT number: 2021-003509-23; ClinicalTrials.gov NCT05299242.


Methods and analysis
We are conducting a multi-centre, randomised feasibility study, with an embedded qualitative sub-study.We will recruit adults ≥18 years with a new episode of shoulder pain attributable to early stage frozen shoulder, recruited from at least five UK NHS musculoskeletal and related physiotherapy services.Participants (n=84) will be randomised Any reports and responses or comments on the (centralised computer generated 1:1 allocation) to receive either: 1) intra-articular injection of anti-TNF (adalimumab 160mg) or 2) placebo injection (saline [0.9% sodium chloride]), both under ultrasound guidance.A second injection of the allocated treatment (adalimumab 80mg) or equivalent volume of placebo will be administered 2-3 weeks later.All participants will receive a physiotherapy advice leaflet providing education and advice about frozen shoulder and pain management.The primary feasibility objectives are: 1) the ability to screen and identify potential participants with pain predominant early stage frozen shoulder; 2) willingness of eligible participants to consent and be randomised to intervention; 3) practicalities of delivering the intervention, including time to first injection and number of participants receiving second injection; 4) standard deviation of the Shoulder Pain and Disability Index (SPADI) score and attrition rate at 3 months (i.e. 12 weeks) post-randomisation in order to estimate the sample size for a definitive trial.We will also assess follow up rates and viability of patient-reported outcome measures and range of shoulder motion for a definitive trial.Research Ethics Committee approval (REC 21/NE/0214).
The aim of this study is to find out if it is possible to run a larger trial to test whether an injection of adalimumab can reduce pain and prevent the disease from getting worse, if given during the early painful phase of frozen shoulder.We need to conduct this smaller study first to be sure it's possible to identify and treat people with early-stage frozen shoulder within the current NHS system, before we conduct a much larger trial to find out if this treatment works.
In this study we will include 84 adults with painful early stage frozen shoulder who have not yet received treatment.People will be randomised to receive either an injection of the drug adalimumab or a dummy injection of saline (placebo) directly into the shoulder joint, both guided by ultrasound.All participants will also receive standardized advice on how to manage their shoulder pain.We will assess participants before treatment and three months later.

Amendments from Version 1
We have revised our protocol to take into account the helpful suggestions made by the reviewer comments.The main changes are: i) clarification that follow up is at 3 months (i.e. 12 weeks) post-randomisation; ii) rewording of the eligibility criteria from "Men and women aged 18 years and above" to be more inclusive "People aged 18 years and above"; iii) rewording of the plain language summary so that the explanation for the use of adalimumab comes before the description of the trial; iv) updating reference to the Outcome Measures in Rheumatology (OMERACT) 2016 core outcome set for shoulder disorders to the finalised and endorsed by OMERACT in 2019; v) updating Figure 1 to clarify that the second injection is delivered 2-3 weeks after the first injection.
Any further responses from the reviewers can be found at the end of the article

Plain language summary
Frozen shoulder is a common condition affecting approximately 9% of people aged 25-64 years.During the early phase the pain is usually unbearable and the later restriction in movement is severely limiting.It occurs when the flexible tissue (capsule) that surrounds the shoulder joint becomes inflamed, thickened and tight.It's not fully understood why this happens but it is more common in people with diabetes or Dupuytren's disease, which causes the fingers to curl into the palm.It can also occur following shoulder injury or surgery.The pain can be very severe and lasts 3-9 months, followed by a 4-12 month period of increasing stiffness, after which the condition usually improves.
Frozen shoulder often affects a person's ability to sleep, carry out everyday activities, and work.Current treatments include rest, painkillers, anti-inflammatories, physiotherapy and steroid injections.If stiffness persists, surgery is sometimes recommended.However, there is no evidence that any of these treatments lead to significant benefit in the long term, with many being ineffective.Steroid injections only help in the short term.Adalimumab has been used very successfully to treat other inflammatory diseases such as rheumatoid arthritis.More recently, adalimumab has also been used to treat Dupuytren's disease, where we found it helps to stop the cells causing the disease and softening and shrinking the diseased diseased tissue.The biological processes underlying frozen shoulder are similar to those in Dupuytren's disease.
The aim of this study is to find out if it is possible to run a larger trial to test whether an injection of adalimumab can reduce pain and prevent the disease from getting worse, if given during the early painful phase of frozen shoulder.We need to conduct this smaller study first to be sure it's possible to identify and treat people with early-stage frozen shoulder within the current NHS system, before we conduct a much larger trial to find out if this treatment works.
In this study we will include 84 adults with painful early-stage frozen shoulder who have not yet received treatment.People

Introduction
Frozen shoulder (adhesive capsulitis) is an extremely painful and debilitating condition and affected individuals struggle with activities of daily living and significant sleep disturbance as a result of severe pain 1 .The condition is very common, affecting about 9% of people in the UK aged 25-64 years 2 , and 20% develop the same problem in the other shoulder 3 .
Frozen shoulder may develop as a primary condition or secondarily following surgery or trauma.Up to 30% of patients with diabetes mellitus develop frozen shoulder and the symptoms are more persistent and recalcitrant in this group 1 .
The classic description of the development of frozen shoulder is of three overlapping phases 4,5 .The initial pain predominant inflammatory phase is characterised by constant pain and difficulty sleeping, and lasts between three and nine months.This progresses to a stiffness predominant fibrotic stage with progressive restriction of motion, particularly external rotation and elevation of the shoulder, and impairment of function, and lasts between four and 12 months.The pain changes from being constant to being manifest at the end of range of motion and of reduced intensity.There is a gradual improvement in range of motion and stiffness over a 12-48 month period, although end of range pain may persist.The average duration of the condition is 30 months (range 1 to 3.5 years) 6 .Full resolution of symptoms does not always occur.
The aetiology of frozen shoulder is poorly understood and consequently there is no consensus on the optimal treatment.The majority of patients with early stage pain predominant frozen shoulder are managed in primary care or at primary care interface musculoskeletal services by physiotherapists and GPs.During this stage, standard treatment consists of rest, advice, analgesics, physiotherapy and corticosteroid injections to address the symptoms.
There is limited efficacy for the treatments currently offered to patients with frozen shoulder.Two Cochrane reviews have concluded that whilst oral steroid or local steroid injections lead to short term benefit in pain and range of motion, the effects are not maintained beyond six weeks [7][8][9] .Other Cochrane reviews concluded that there is no evidence that physiotherapy or ultrasound therapy are beneficial 10 , and that manual therapy with exercise is less effective than corticosteroid injection in the short term 11 .These findings are supported by a Health Technology Assessment report which found that, of all treatment options available, the only short-term benefit was from steroid injection in addition to home exercise in patients with symptoms of less than six months 12 .In addition, manipulation under anaesthesia was found to be no better than home exercise programme 12 , and the use of arthrographic joint distention with glucocorticoid and saline was no better than sham procedure 13 .The United Kingdom Frozen Shoulder Trial (UK FROST) compared the effects of physiotherapy plus corticosteroid injection, manipulation under anaesthesia with a steroid injection, and arthroscopic capsular release supplemented with a steroid injection 9 .None of the treatments were found to be clinically superior.In addition, UK FROST recruited patients from secondary care, and it was unlikely that people in the initial pain predominant inflammatory phase were included.
Our study (Anti-Freaze-F) is designed to specifically target people with early stage pain predominant frozen shoulder.We will assess the feasibility of conducting a large multicentre randomised trial to test whether giving an intra-articular injection of adalimumab (a drug targeting the inflammatory mediator tumour necrosis factor [TNF]), can reduce pain and prevent the disease from getting worse, if given during the early pain predominant stage (i.e., within approximately three months of onset of symptoms).Whilst the pathogenesis of frozen shoulder remains largely unknown, a recent systematic review confirmed the presence of fibrosis and the role of inflammation 6 .The affected tissues are infiltrated by immune cells, including macrophages, mast cells, T cells, and there are elevated levels of pro-inflammatory cytokines, including TNF, IL-6 and IL-1ß 14,15 , with myofibroblasts contributing to the deposition of excessive matrix components that result in fibrosis 16 .More than 50% of people with frozen shoulder also have Dupuytren's disease 17 and the underlying pathology of frozen shoulder is similar to Dupuytren's disease 16,18 where our laboratory studies have shown that the myofibroblast phenotype is critically dependent on the local production of low levels of the pro-inflammatory cytokine TNF 19 .In a dose-ranging proof of concept phase 2a and 2b clinical trial (RIDD trial) we found that local injection of 40mg of adalimumab in 0.4ml directly into Dupuytren's nodules resulted in downregulation of the myofibroblast phenotype 20,21 .
Anti-TNF drugs have a very strong safety profile, having been used in over 10 million people, adalimumab in over five million, and more than 25,000 patients have been recruited to trials of adalimumab, which is approved for nine different disorders.Adalimumab is not currently licenced for use as an intra-articular injection for pain predominant early-stage frozen shoulder and therefore will be used off license for the purposes of this trial.If successful, the Anti-Freaze-F trial could provide evidence that it is feasible to conduct a trial of Anti-TNF for a very common debilitating shoulder condition, avoiding the need for surgery and prolonged physiotherapy, thereby reducing National Health Service (NHS) cost.

Objectives
The aim of the Anti-Freaze-F trial is to assess the feasibility of conducting a large randomised controlled trial to assess whether an intra-articular injection of adalimumab (anti-TNF) can reduce pain and improve function in people with early stage frozen shoulder.
The primary objectives of this feasibility study are to assess the: • ability to screen and identify potential participants with pain predominant early stage frozen shoulder; • willingness of eligible participants to consent and be randomised to intervention; • practicalities of delivering the intervention, including time to first injection and number of participants receiving second injection; • standard deviation (SD) of the Shoulder Pain and Disability Index (SPADI) score and attrition rate at 3 months (i.e. 12 weeks) post-randomisation in order to estimate the sample size for a definitive trial.
Secondary objectives are to assess the follow up rates and viability of patient reported outcome measures and clinician assessed range of shoulder motion at 3 months (i.e. 12 weeks).Patient reported outcomes include pain and shoulder function, participant assessed range of shoulder motion, psychological factors, sleep disturbance, return to desired activities, global impression of change and health resource use.An embedded qualitative sub-study will be conducted to explore participants' experiences of being recruited into the trial.

Study design
The trial will be a multi-centre, randomised, double blind, parallel group, feasibility trial, with an embedded qualitative sub-study (Figure 1).

Setting
The trial will be conducted across at least five NHS primary and or secondary-care-based musculoskeletal services and their related physiotherapy services, dependant on the local service provision.These services treat people with a range of musculoskeletal conditions and are run by specialist practitioners including extended-scope physiotherapists, general practitioners (GP) with a specialist interest in musculoskeletal conditions, rheumatologists, and orthopaedic surgeons.

Study participants
Participants with a new episode of shoulder pain attributable to pain predominant stage of frozen shoulder will be recruited from NHS primary-care-based musculoskeletal services and their related physiotherapy services, with treatment delivered within these services or the local secondary care site dependant on the local service provision.Participants may also be recruited from directly from NHS secondary-care-based musculoskeletal services, dependant on local service provision at sites.Imaging, including plain radiographs, may be used to confirm the diagnosis of frozen shoulder and rule out other pathology such as glenohumeral arthritis 22 as per standard NHS care (i.e.not as part of trial procedures).

Eligibility
Patients will be eligible for this study if they are: • People aged 18 years and above; • with a new episode of shoulder pain attributable to pain predominant stage of frozen shoulder (i.e.within approximately three to nine months of onset of symptoms) diagnosed using criteria set out in the British Elbow and Shoulder Society (BESS) guidelines 23 ; • who are not being considered for surgery; • able to understand spoken and written English; • willing and able to give informed consent for trial participation and comply with all study requirements and timeline; • willing to allow their GP to be notified of participation in the trial; • if female, and of child-bearing potential and willing to use effective contraception throughout the treatment period and for five months after the last injection.
We will exclude those: • with frozen shoulder secondary to significant shoulder trauma (e.g., dislocation, fracture or full thickness tear requiring surgery) or other causes (e.g., recent breast cancer surgery or radiotherapy); • with a neurological disease affecting the shoulder; • with bilateral early stage frozen shoulder; • with other shoulder disorders (e.g., inflammatory arthritis, rotator cuff disorders, glenohumeral joint instability) or with red flags consistent with the criteria set out in the BESS guidelines 23 ; • who have received corticosteroid injection for shoulder pain in the last 12 weeks to either shoulder; • currently taking any anti-TNF drug, or being treated with coumarin anticoagulants, such as warfarin; • who have participated in another research study involving an investigational medicinal product in the past 12 weeks; • with significant renal or hepatic impairment; • with contra-indications to anti-TNF injection; • with any other significant disease which, in the opinion of the Investigator, may either put the participants at risk because of participation in the study, or may influence the result of the study.

Recruitment of participants, screening and eligibility assessment
Potential participants will attend their appointment in accordance with standard NHS procedures at each site.The treating practitioner will undertake a clinical assessment according to their usual practice.If a patient fulfils the criteria for pain predominant stage of frozen shoulder, they will be assessed to see whether they meet the Anti-Freaze-F eligibility criteria.Patients will be provided with a copy of the participant information sheet and asked if they wish to participate in the trial.Those meeting the eligibility criteria and wishing to participate in the trial will be approached for informed consent.Patients who do not meet the eligibility criteria, or who do not wish to participate will receive standard NHS treatment.We will record anonymised information on the age and sex of those who decline to participate so that we can assess the generalisability of those screened.The reasons for declining will be asked and any answers given will be recorded.
Informed consent, baseline assessment and trial specific screening tests After participants have been assessed for eligibility, informed consent for participation in the trial will be sought by a research facilitator trained in good clinical practice.The process for seeking, confirming and documenting informed consent will be either paper based (written consent) or digital (e-consent) depending on local facilities at each site.Participants will then be asked to complete the baseline assessment questionnaire that will record demographic information and baseline measurements for the patient reported outcome measures (Table 1 and Table 2).The questionnaires will be available in both online and paper formats as, due to their frozen shoulder, participants may find one format much easier to complete than the other.Clinician assessed baseline measurement of range of motion of the shoulder will also be performed.
Participants will undergo serological testing to check for latent Tuberculosis (TB) and Hepatitis B surface antigen.Blood tests will be performed during the baseline assessment or at the time the participant attends for their first injection appointment (depending on the local site provision).The risks of

Global impression of treatment
Patient-rated Likert scale 29 3 months

Return to desired activities
Patient-reported return to desired activities, including work, social life and sport activities 30 3 months Health resource use Consultation with primary and secondary care, additional physiotherapy, injection use, or alternative therapies for index shoulder

months
Adverse Events Any Grade 3 or above AEs that have occurred from Consent up until the 3 month Follow up.

months
reactivation following a single injection are low; any participant for whom the serology test result shows positive will be referred to their local infectious diseases service and will not receive the second injection.

Randomisation
Consented participants will be randomised to intervention groups (1:1) by the site research facilitator using the centralised randomisation service provided by the Oxford Clinical Trials Research Unit.Randomisation will be computer-generated and stratified by study site using a variable block size to ensure the participants from each study site have an equal chance of receiving either intervention.

Blinding
Study participants and site staff, except pharmacy staff, will be blinded to treatment allocation.The clinician delivering the treatment injection will not be blinded but will not be involved with any further trial-specific assessment of the participant.The trial statistician and data entry personnel will not be blinded to the treatment allocation.The remaining members of the trial management team, including the staff conducting the qualitative interviews, will be blinded to treatment allocation until after data analysis is complete.

Adalimumab/Placebo Injection
Eligible participants will be allocated to receive either an intraarticular injection of adalimumab (160mg in 3.2ml for the first injection, 80mg in 1.6ml for second injection) or placebo (normal saline [0.9% sodium chloride] 3.2ml for the first injection and 1.6ml for the second injection).The dose of 160mg followed by 80mg two weeks later was selected as this is the approved loading dose in patients with inflammatory bowel disease 31 .
The injection will be given approximately within two weeks of randomisation into the anterior shoulder joint space in the rotator cuff interval where there is maximal inflammation of the capsule and synovium 32 , under guided ultrasound by an appropriately qualified practitioner.The practitioner will be either a GP with a specialist interest in musculoskeletal conditions, rheumatologist, extended scope physiotherapist, orthopaedic surgeon, sonographer or radiologist, dependant on the local service provision at study sites.The practitioner will confirm the participant is still in the pain predominant phase before administering the first injection.If the participant is no longer in the pain predominant phase, they will not receive the injection and the reason will be recorded.
We will use adalimumab in vials supplied by Fresenius Kabi Ltd (Idacio 40mg/0.8ml) rather than a pre filled syringe or pen as the needles fitted to the pre-filled syringes are too short for shoulder joint injection.The adalimumab/placebo injection will be dispensed by the local site pharmacy and sealed in identical sized and sealed opaque plastic bags in order to maintaining blinding by staff who are blinded to treatment allocation.Preparation of the adalimumab/placebo injection will take place in a clinic room/area separate from the participant to ensure the participant remains blinded to their treatment allocation immediately prior to injection.Both adalimumab and placebo have a similar viscosity and appearance so the two treatments will be indistinguishable.The same type of syringe and needle will be used for injection of both adalimumab and saline thus maintaining the blinding of the participant and staff not involved in preparation and administration of the injection.The skin at the site of injection of adalimumab/placebo may be infiltrated with local anaesthetic to reduce the pain of the injection in accordance with local practice.Once adalimumab has been drawn up, it tends to lose it potency and this precludes preparation of the syringes before the patient presents for treatment.For this trial, no more than 30 minutes will elapse from when the injection is drawn up from the vials to when the injection is given.
All participants irrespective of whether they are still in the pain predominant phase, will receive a second injection (adalimumab/placebo) administered 2-3 weeks after the first injection, unless the participant declines the second injection, has a related grade 3 or above adverse event after the first injection or tests positive for TB or hepatitis B surface antigen.Injection details, including time from randomisation to injection delivery, will be recorded on a trial specific injection treatment log.Participants will be advised they can continue with their physiotherapy and resume normal day-to-day activities immediately after the injection.Participants will be provided with a written information leaflet advising them that there will be no restriction on their activities after the injection and what to do if they experience any side effects.

Physiotherapy advice leaflet
All participants will receive a written physiotherapy advice leaflet providing education and advice about frozen shoulder and pain management 4 .Physiotherapy during the early pain predominant stage of frozen shoulder is primarily directed at pain relief (e.g., heat, cold and other pain relieving modalities) as forcing the joint to move can make it more painful and is best not pursued.Participants will be advised to take over-the-counter analgesia as required, in accordance with the BESS guidelines 23 .They will be provided with advice on modifying activities that exacerbate symptoms and on sleeping positions 33 .The advice leaflet will also include simple self-guided exercises, which participants can use to increase shoulder joint mobilisation, once the early pain predominant stage reduces.Exercises include passive mobilisation of the shoulder and capsular stretching 9 .Joint mobilisation combined with stretching exercises has been found to be more effective than stretching exercises alone 34,35 .As low health literacy levels are a major consideration when developing patient-facing materials, plain English and patient representative involvement will be used to optimise readability.

Concomitant care
Participants may seek other forms of treatment during the follow-up period of the trial but will be informed that they should use usual routes (e.g., through GP referral) to do so.Additional treatments, including consultation with their GP or other health professional will be recorded.

Feasibility objectives
The main aim of this feasibility study is to determine whether a future definitive trial would be feasible and to determine the sample size for the definitive trial to assess the effectiveness of anti-TNF adalimumab.We will focus on the main areas of uncertainty relating to the acceptability to be randomised to intra-articular injection of adalimumab and the ability to identify and recruit and treat participants who have pain predominant early stage frozen shoulder within the current NHS patient pathway for musculoskeletal conditions.In addition, we will collect outcome measures at three months (i.e. 12 weeks), including SPADI and range of shoulder motion.To determine the feasibility of a definitive randomised controlled trial, the success criteria will be: • Ability to screen and identify potential participants with pain predominant stage frozen shoulder.
• Willingness of eligible participants to consent and be randomised to intervention.
• Practicalities of delivering the intervention, including time to first injection and number of participants receiving second injection.
Data to assess our feasibility objectives will be collected at each site via a trial specific screening log; reasons for ineligibility and/or participants declining to participate in the trial will be recorded where available.Injection details, including time from randomisation to injection delivery, will be monitored based on the information recorded on the trial specific injection treatment logs.

Outcomes
Outcomes (Table 1) will be collected at baseline and at three-months (i.e 12 weeks) to assess the feasibility of collecting these in a future definitive trial and to obtain the variability estimates required for estimation of the sample size of the definitive trial.Patient reported outcomes will include shoulder pain and function measured using the SPADI scale (primary outcome for definitive trial) 24,25 ; sub-domains of pain (SPADI 5-item pain subscale), function (SPADI 8-item disability subscale) 24,25 ; shoulder range of motion (Participant Shoulder Movement Questionnaire); psychological factors (Fear Avoidance Belief Questionnaire) 26 ; pain self-efficacy questionnaire 27 ; sleep disturbance (Insomnia Severity Index) 28 ; patient global impression of change 29 ; return to desired activities; additional health resource use for index shoulder (e.g.consultation with primary and secondary care, additional physiotherapy, injection use, or alternative therapies).The choice of outcome measures is based on Outcome Measures in Rheumatology (OMERACT) 2019 core outcome set for shoulder disorders 36 and a systematic review of core outcomes used in studies of frozen shoulder 37 .
At baseline and three month (i.e. 12 weeks) follow up, a blinded assessor will use a universal manual goniometer to measure range of shoulder movements, including active flexion, extension, abduction internal and external rotation, limitation of which has been shown to be pathognomonic of frozen shoulder in the absence of glenohumeral arthritis 38 .

Adverse events
The safety profile of adalimumab is well known, with the most common adverse reactions being mild injection site reactions.The Common Terminology Criteria for Adverse Events (CTCAE) v5.0 will be used to guide recording adverse events including grading of the event.Only clinician assessed adverse events, graded 3 and above, occurring during the trial for each participant, from their consent until the three month (i.e 12 weeks) follow up and that are considered related to the trial medication (adalimumab/placebo) will be recorded.
Participants will be asked by the treating clinician at their second injection visit if they have experienced any adverse events as a result of their first injection.Similarly, participants will be asked if they have experienced any adverse events as a result of their second injection at the three month follow up appointment.
Follow up data collection Follow up will be conducted via face-to-face clinic assessment and patient reported questionnaire at three months after randomisation (Table 1).Participants who are unable to attend the face-to-face appointment will be asked to complete the questionnaire and return it to the Anti-Freaze-F trial office in a prepaid envelope or submit online as appropriate.The reason why a participant is unable to attend the face-to-face clinic appointment will be recorded and whether this was due to potential COVID-19 restrictions or other reasons.For those who do not respond, at least one reminder will be sent.Telephone and email follow-up will also be used to contact those who do not respond to the reminder or who have not fully completed the returned questionnaire.

Data management
All data will be processed according to the UK General Data Protection Regulations (GDPR) and the Data Protection Act 2018.All documents will be stored safely in confidential conditions.A data management and sharing plan will be prepared for the trial and will include reference to confidentiality, access and security arrangements.All trial-specific documents, except for the signed consent form and follow-up contact details, will refer to the participant with a unique study participant number/code and not by name.Trial data will be collected and managed using REDCap (Research Electronic Data Capture) electronic data capture tools hosted at the Oxford Clinical Trials Research Unit, University of Oxford.REDCap is a secure, web-based application.

Sample size
The main feasibility objective and therefore the basis of the sample size estimate is participant recruitment from at least five centres with a staggered start.The target sample size is 84 participants, equivalent of one to two participants per month per site over 12 months, allowing for staggered opening of sites.Seventy is the recommended minimum target sample size when including an estimate of the SD in an external pilot trial 39 .The sample size has been increased from 70 to a total of 84 participants in order to increase precision of the estimate of the standard deviation of SPADI at 3 months, the proposed primary outcome for the definitive trial, and to take into account possible attrition (based on an attrition rate of 15%).This attrition rate is a conservative estimate based on attrition rates for the GRASP (14% at six months) 33 and UK FROST (11% at three months) 9 trials, which represent similar populations to those anticipated in Anti-FREAZE-F.This sample size will enable an estimate of a participation rate of 30% with a precision of +/-5% based on 280 eligible participants being identified.We have selected a conservative recruitment rate given the uncertainty around the ability to identify, recruit and inject participants with early stage frozen shoulder.

Statistical methods
Feasibility outcomes will be reported, including the number of participants approached, those eligible, consenting to randomisation and follow-up, the delivery of intervention (including time to first injection), withdrawal rate, the number receiving a second injection (per group and overall) and data completeness.Baseline characteristics (including possible stratification factors for the definitive trial) will be reported using descriptive statistics, separately per group and overall either using the mean and SD or median and inter-quartile range (if not normally distributed) for continuous variables and the number and percentage of participants in each group for categorical variables.All statistical analyses will be carried out using Stata (current version).Measures of central location and dispersion of clinical and patient reported outcome measures, including health resource use, at three months will be reported and differences between treatments for the intention-to-treat population (i.e., the population of participants as randomised) will be reported with 95% confidence intervals.The SD of the proposed primary outcome, SPADI at three months (i.e. 12 weeks), will be used to inform an estimation of the sample size required for the definitive trial.An estimate of treatment effectiveness will be reported together with the 95% confidence interval.This along with change from baseline in range of shoulder motion at three months (i.e. 12 weeks) will provide an indication of potential efficacy of the intervention but will not be powered to provide a definitive result, which will only follow the fully powered definitive main trial.Even small increases in range of shoulder motion are important to people with frozen shoulder, where pain and restricted shoulder movement can be very debilitating.Therefore, we will use a 10-degree improvement in active flexion with any associated improvement in active external rotation of the shoulder to mean a potentially important difference 40 .If we observe this difference between groups in our feasibility study with short follow up and a small sample this would indicate potential efficacy, which should then be formally, tested in the full trial.Adverse events graded 3 or above will be summarised per group and overall in all participants.

Embedded qualitative study
The aims of the qualitative sub-study are to explore the participants' experiences of being recruited to a randomised trial of anti-TNF injection for frozen shoulder, of the treatment received and follow-up schedule, and to understand what helps participant recruitment to the trial intervention.We will interview a purposive sample of up to 15 participants (or until we reach data saturation) to provide variability for age, gender, ethnicity and geographical representation.Participants will be invited to receive further information about the qualitative sub-study at the time of consent to the main trial.
Individual telephone interviews will be conducted within four weeks of either intervention delivery by a qualitative researcher blinded to the intervention) using a semi-structured interview guide with open-ended questions.

Progression criteria
Progression criteria for the future definitive trial will be judged using a traffic light system whereby 'Green' indicates it is feasible to proceed to a definitive trial with the current procedures, 'Amber' indicates modification to one or more aspect of the study is required before proceeding to the future definitive trial, and 'Red' indicates it is not feasible 41 .The decision to progress to a future definitive trial will be made by the Trial Management Group in conjunction with the Trial Oversight Committee, based on the criteria in Table 3.It will also be informed by findings from the embedded qualitative sub-study and any potential signal of efficacy with improvements in range of shoulder motion as a result of anti-TNF injection.
expertise to confirm that it is of an acceptable scientific standard.

Version 1
Reviewer Report 03 April 2023 https://doi.org/10.3310/nihropenres.14394.r29120 © 2023 Siebert S. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Stefan Siebert
School of Infection and Immunity, University of Glasgow, Glasgow, Scotland, UK The authors present a protocol for multi-centre, randomised, double-blind feasibility study of intra-adalimumab adalimumab injections for early frozen shoulder.The protocol is very well written, with clear justification and methods that address the primary objectives.
Importantly for a feasibility study, the progression criteria for the main study are clearly predefined.
I have a few comments, relating to some aspects where the protocol is slightly unclear or not specific: 1. Timing of follow-up/final outcome and Table 2: The final assessment is at 3 months but it appears from Table 2 that this is 3 months from screening rather than first injection.I would have expected the latter in light of the variable timing from screening to 1 st injection (meaning some participants may only have 10 weeks from injection) and this may be what is intended, although I note assessments are only done at screening.Either way, the authors should clearly indicate the timepoint for screening in order for others to be able to replicate this work: i.e. either ["Screening week 0"] or ["Screening week -2 to 0" and "1 st injection = week 0"].
It would also be more typical and helpful to express this final outcome timing in weeks (i.e. 12 weeks) rather than months in order to avoid potential confusion relating to whether this is 3 calendar months or 12 weeks.
2. It is also unclear from the protocol what would occur if >2 weeks passed from screening to 1 st injection.This is particularly import as ITT analysis based on randomization so need to know if would be withdrawn, rerandomized etc.The same applies to what would occur if >3 weeks between 1 st and 2 nd injection visit -I assume no injection would be given but actions for both scenarios should be clearly stated.
3. As a CT-IMP, I would have expected standard adverse event reporting requirements to apply.
4. Eligibility criteria -timing from symptom onset: It is unusual to include an "approximate" cut-off in inclusion criteria as this introduces potential variability, both within this study and with replication studies.I presume this was included to facilitate recruitment, and may be acceptable for this feasibility study (provided clearly and rigorously recorded), but it is largely meaningless without some upper limit (is 4 months ok, what about 5 months?) and would not be acceptable for the main study.
5. Eligibility criteria -frozen shoulder diagnosis: I found the inclusion criteria slightly vague and open to interpretation.I would have expected more formal diagnostic criteria for frozen shoulder for an RCT.While I accept this study may be intended to reflect real-world-practice, if the authors propose to use results from this and/or the subsequent main study to obtain approvals for this treatment (adalimumab is not currently licensed for intra-articular injection), I would recommend early discussions with the relevant regulatory bodies to ensure they would accept these criteria for licensing purposes.
I look forward to seeing the results of this important study in the future.
Is the rationale for, and objectives of, the study clearly described?Yes

Are sufficient details of the methods provided to allow replication by others? Partly
Are the datasets clearly presented in a useable and accessible format?

Not applicable
Competing Interests: No competing interests were disclosed.
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.RESPONSE: This is a feasibility study and so one of our main feasibility objectives is to assess the practicalities for trial sites to deliver the intervention, including the time to first injection and number of participants receiving second injection.This information would then be used to inform any future definitive trial.Therefore, we would respectfully submit that the issue of ITT analysis is not applicable here.

As a CT-IMP, I would have expected standard adverse event reporting requirements to apply.
RESPONSE: Procedures for recording adverse events are described in the protocol in the section "Adverse events".We will record clinician assessed adverse events, graded 3 and above, occurring during the trial for each participant, from their consent until the three month (i.e. 12 weeks) follow up and that are considered related to the trial medication (adalimumab/placebo).
4. Eligibility criteria -timing from symptom onset: It is unusual to include an "approximate" cutoff in inclusion criteria as this introduces potential variability, both within this study and with replication studies.I presume this was included to facilitate recruitment, and may be acceptable for this feasibility study (provided clearly and rigorously recorded), but it is largely meaningless without some upper limit (is 4 months ok, what about 5 months?) and would not be acceptable for the main study.
RESPONSE: Recruitment will be based on the participant's predominant symptom being pain rather than limitation of movement or function.The duration of the pain-predominant phase can be very variable, usually between 3 -9 months and, therefore it is difficult to precisely stipulate inclusion based on a precise time period.We have now clarified this in the protocol.

Eligibility criteria -frozen shoulder diagnosis: I found the inclusion criteria slightly vague and
open to interpretation.I would have expected more formal diagnostic criteria for frozen shoulder for an RCT.While I accept this study may be intended to reflect real-world-practice, if the authors propose to use results from this and/or the subsequent main study to obtain approvals for this treatment (adalimumab is not currently licensed for intra-articular injection), I would recommend early discussions with the relevant regulatory bodies to ensure they would accept these criteria for licensing purposes.
RESPONSE: We used the BESS (British Elbow and Shoulder Society) criteria for diagnosis of pain predominant early phase frozen shoulder, which is widely used by physiotherapists and shoulder specialists within the NHS.In the protocol we state that imaging, including plain radiographs, may be used to confirm the diagnosis of frozen shoulder and rule out other pathology such as glenohumeral arthritis as would happen as per standard NHS care (i.e.not as part of trial procedures).Regulatory approval from the MHRA was successfully obtained for the trial.
there needs to be a clearer link between the first and second paragraph.The first paragraph ends with the claim that there is no evidence that current treatments, including rest, painkillers, antiinflammatories, physiotherapy and steroid injections lead to significant benefit in the long term, and that steroid injections only help in the short term.Then in the second paragraph the authors claim that the aim of the study is to find out if it is feasible to "run a larger trial to test whether an injection of adalimumab can reduce pain and prevent the disease from getting worse".However, it's not clear why the authors are investigating the effects of adalimumab, nor what adalimumab even is (is it a type of one of the interventions described as ineffective in the first paragraph, or something else entirely?).
Postscript: Oh, I see a rationale for the choice of adalimumab appears at the end of the third paragraph.Hmm, I think it would flow better if this text were moved earlier.
Eligibility: By specifying that "Men and women aged 18 years and above" were eligible for this study, does this mean that non-binary people and those who do not identify with either of those genders are ineligible?If not, perhaps it's more inclusive to just write "People aged 18 years and above".Eligibility: By specifying that "Men and women aged 18 years and above" were eligible for this study, does this mean that non-binary people and those who do not identify with either of those genders are ineligible?If not, perhaps it's more inclusive to just write "People aged 18 years and above".

RESPONSE:
We have reworded this as suggested to be more inclusive.RESPONSE: We have changed Figure 1 to clarify the second injection is given 2-3 weeks after the first injection.We have also clarified that follow up is 3 months (i.e. 12 weeks) postrandomisation.
Informed consent, baseline assessment and trial specific screening tests: It is not immediately clear to me why "Participants will undergo serological testing to check for latent Tuberculosis (TB) and Hepatitis B surface antigen".
RESPONSE: Continuous administration of anti-TNF is associated with reactivation of latent TB or hepatitis B. Whilst the risk is extremely low following a single injection, to ensure participant safety we specified that participants will undergo serological testing before the second injection.Those testing positive will be referred to their local infectious diseases service and will not receive the second injection

1 st* 2
Anti-TNF/placebo injection ✓ Physiotherapy advice leaflet provision ✓ 2 nd Anti-TNF/placebo injection* ✓ ASSESSMENTS: Serological testing e.g.TB ELISpot, Hepatitis B surface antigen ✓ Pregnancy testing (if needed) nd injection must be 2-3 weeks after the 1 st injection **interview conducted within 4 weeks of intervention delivery

Figure 1 :
Figure 1:It might help to clarify that the second injections will be delivered 2-3 weeks after the first injection.It would also help to specify if follow-up is at 3-months from randomisation, or 3months after receiving the second injection.

Figure 1 :
Figure 1: It might help to clarify that the second injections will be delivered 2-3 weeks after the first injection.It would also help to specify if follow-up is at 3-months from randomisation, or 3months after receiving the second injection.

Table 1 . Outcomes and time points of assessment. Outcome Measurement Time point Demographic
Age, Sex, Height, Weight, Ethnicity, Smoking, Date of frozen shoulder diagnosis, Duration of symptoms, Hand dominance, Affected shoulder, Diabetes and type, Dupuytren's

Table 2 :
The final assessment is at 3 months but it appears from Table 2 that this is 3 months from screening rather than first injection.
RESPONSE: Reporting of the outcome measures is at 3 months (i.e. 12 weeks).We have clarified this in the protocol.2.It is also unclear from the protocol what would occur if >2 weeks passed from screening to 1 st injection.This is particularly import as ITT analysis based on randomization so need to know if would be withdrawn, rerandomized etc.The same applies to what would occur if >3weeks between 1 st and 2 nd injection visit -I assume no injection would be given but actions for both scenarios should be clearly stated.

Table 2 :
Love this table, really helpful!Outcomes:The authors claim that "The choice of outcome measures is based on Outcome Measures in Rheumatology (OMERACT) 2016 core outcome set for shoulder disorder".However, the core outcome set cited is a preliminary core outcome set, which was finalised and endorsed by OMERACT in 2019.So I suggest the final core outcome set be cited -Ramiro et al. (2019)1.

Are the datasets clearly presented in a useable and accessible format? Not applicable Competing Interests:
No competing interests were disclosed.

Table 2 :
Love this table, really helpful!RESPONSE: Thank you!Outcomes: The authors claim that "The choice of outcome measures is based on Outcome Measures in Rheumatology (OMERACT) 2016 core outcome set for shoulder disorder".However, the core outcome set cited is a preliminary core outcome set, which was finalised and endorsed by OMERACT in 2019.So I suggest the final core outcome set be cited -Ramiro et al. (2019) 1 .
RESPONSE:We have updated this reference.