Subacromial spacers for adults with symptomatic, irreparable rotator cuff tears: the START:REACTS novel group sequential adaptive RCT
Authors: Metcalfe Andrew , Arnold Susanne , Parsons Helen , Parsons Nicholas , Bhabra Gev , Brown Jaclyn , Bush Howard , Diokno Michael , Elliott Mark , Fox Josephine , Gates Simon , Gemperlé Mannion Elke , Haque Aminul , Hutchinson Charles , Kearney Rebecca , Khan Iftekhar , Lawrence Tom , Mason James , Rahman Usama , Stallard Nigel , Ul-Rahman Sumayyah , Viswanath Aparna , Wayte Sarah , Drew Stephen , Underwood Martin 
Published: September 2023

Background
A balloon spacer is a relatively simple addition to an arthroscopic debridement procedure for irreparable rotator cuff tears.

Objective
To evaluate the clinical and cost-effectiveness of a subacromial balloon spacer for individuals undergoing arthroscopic debridement for irreparable rotator cuff tears.

Design
A multicentre participant-and assessor-blinded randomised controlled trial comparing arthroscopic debridement with the InSpace® (Stryker, Kalamazoo, MI, USA) balloon to arthroscopic debridement alone, using a novel adaptive design. Pretrial simulations informed stopping boundaries for two interim analyses, using outcome data from early and late time points.

Setting
A total of 24 NHS centres.

Participants
Adults with a symptomatic, irreparable rotator cuff tear for whom conservative management had been unsuccessful.

Interventions
Arthroscopic debridement of the subacromial space plus insertion of the InSpace balloon compared with arthroscopic debridement alone.

Main outcome measures
Oxford Shoulder Score at 12 months.

Results
A predefined stopping boundary was met at the first interim analysis. Recruitment stopped with 117 participants randomised. We obtained primary outcome data on 114 participants (97%). The mean Oxford Shoulder Score at 12 months was 34.3 in the debridement-only group (59 participants of 61 randomised) and 30.3 in the debridement with balloon group (55 participants of 56 randomised; mean difference: −4.2; 95% confidence interval −8.2 to −0.26; p = 0.037). There was no difference in safety events. In the cost-effectiveness analysis, debridement-only dominated with a probability of <1% that the device is cost-effective.

Magnetic resonance imaging substudy
To evaluate the function of the balloon, we developed a dynamic magnetic resonance imaging protocol to induce humeral movement by activating the deltoid. The pandemic restricted recruitment, so the sample size was small (n = 17).

Statistical methodology study
We applied the novel adaptive design approach to data from seven previous randomised controlled trials. The method would have been applicable to five of these trials and would have made substantial savings in time to recruitment, without compromising the main findings of the included trials.

Interim analysis interpretation study
We asked potential data monitoring committee members to review interim analysis reports presented using Bayesian and frequentist frameworks. They did not always follow the stopping rules and would benefit from additional information to support decision-making.

Limitations
The InSpace balloon could be beneficial in a different population although we are not aware of it being widely used for other purposes. As a result of the pandemic, we were not able to complete data collection for objective measures.

Conclusions
In this efficient adaptive trial, clinical and cost-effectiveness favoured the control treatment without the InSpace balloon. Therefore, we do not recommend this device for the treatment of irreparable rotator cuff tears.

Future work
There is an urgent need for high-quality research into interventions for people with irreparable rotator cuff tears as there is a lack of good evidence for all available treatment options at present.

Trial registration
This trial is registered as ISRCTN17825590.

Funding
This project (project reference 16/61/18) was funded by the Efficacy and Mechanism Evaluation (EME) Programme, a Medical Research Council and National Institute for Health and Care Research (NIHR) partnership. The trial is co-sponsored by the University of Warwick and University Hospitals Coventry and Warwickshire NHS Trust. This study will be published in full in Efficacy and Mechanism Evaluation; Vol. 10, No 3. See the NIHR Journals Library website for further project information.