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The Big BOSS Study- The British Orthopaedic Slipped Capital Femoral Epiphysis (SCFE) Surgery Study for Severe Stable Slips. A multi-centre prospective randomised superiority trial of an acute deformity correction versus pinning in-situ for severe stable SCFE in children.


For more information on this trial including details on taking part, please visit the dedicated trial website


Slipped Capital Femoral Epiphysis (SCFE) is the most common hip disease of adolescence, akin to a hip fracture. There is strong evidence that childhood obesity is the major cause. In the short-term SCFE requires surgery to stabilise the hip, and typically results in deformity. In the long-term it accelerates the development of osteoarthritis and disability, often necessitating hip replacement in early adulthood. Patients with severe deformity face particular uncertainty.

Traditionally, the approach to managing severe SCFE is to stabilise the hip with minor surgery, albeit accepting the deformity that may cause pain and arthritis. However, increasingly an ‘open reduction’ of the hip is performed to immediately restore normal anatomy, though this comes with the risk of damaging the blood vessles to the hip, which could cause complete collapse of the femoral head with pain and disability.

The growing uncertainty amongst surgeons regarding the optimal surgical approach has prompted members of the British Society for Children’s Orthopedic Surgery to prioritise this question as their most important research priority. Determining the optimal surgical management of severe stable SCFE is important to limit the profound disability that may occur as a consequence of this disease.


This is a multi-centre prospective randomised superiority trial of acute deformity correction versus pinning-in-situ for stable severe SCFE in children aged 8 years and above.


This study will aim to recruit a minimum of 192 patients with stable severe SCFE. It is anticipated that 30 hospitals will become recruiting centres.

After providing consent and baseline data, patients will be fairly allocated (1:1) to either pinning in-situ or acute correction. The randomisation process will be stratified for: age group (8-10 years, 11-16 years) and presence/absence of bilateral disease.

It is expected that routine clinical follow-up will occur at 6-8 weeks, 12 & 24 months. Data collected during these routine visits will be collated by the research team.

All children and young people will be followed-up for two-years to monitor their hip. They will also be asked about pain, if they needed any more surgery, school attendance, any complications, the number of hospital visits, their quality of life and satisfaction with care. Participant follow-up will be organised by the University of Oxford – either electronically by email, text message or by telephone.

An embedded qualitative study will occur throughout the study to inform the development of trial materials and to identify barriers and facilitators to recruitment. This information will be used to develop practical strategies that can be implemented to improve recruitment and enhance acceptability of the trial.

Recruitment period is approximately 3 years.


The aim of this pragmatic randomised controlled trial is to evaluate the clinical and cost-effectiveness of acute correction of deformity, compared to pinning in-situ for the management of severe stable SCFE in children.

The primary objective is to determine whether children treated with acute correction have improved function compared with children treated with pinning in-situ, measured using observed differences in the Patient Reported Outcomes Measurement Information System Mobility Score for Children at two-years post-randomisation.


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