Here is the design of a clinical trial:

Official Title: Comparison of the Clinical and Cost Effectiveness of Two Management Strategies for Non-acute Anterior Cruciate Ligament (ACL) Injury: Rehabilitation Versus Surgical Reconstruction.

Included conditions:
- Anterior Cruciate Ligament Injury

Study Armgroups:
- {'label': 'ACL Rehabilitation Group', 'type': 'EXPERIMENTAL', 'description': 'Non-surgical management \\[Rehabilitation\\] with option for later Anterior Cruciate Ligament (ACL) reconstruction, only if required.', 'interventionNames': ['Other: Non-Surgical Management (Rehabilitation)']}
- {'label': 'ACL Reconstruction Group', 'type': 'ACTIVE_COMPARATOR', 'description': 'Surgical Management - Anterior Cruciate Ligament (ACL) reconstruction surgery', 'interventionNames': ['Procedure: Surgical Management (Reconstruction)']}

Interventions:
- {'type': 'OTHER', 'name': 'Non-Surgical Management (Rehabilitation)', 'description': 'Routine ACL rehabilitation protocols used at the participating site will be followed. As part of the site selection process, documentary evidence of the use of or willingness to adopt a rehabilitation protocol that reflects the guidelines of the mandatory aims/goals set for the study rehabilitation intervention will be required.', 'armGroupLabels': ['ACL Rehabilitation Group'], 'otherNames': ['Physical Therapy', 'Physiotherapy', 'Conservative Rehabilitation', 'Conservative Management']}
- {'type': 'PROCEDURE', 'name': 'Surgical Management (Reconstruction)', 'description': "All surgical reconstructions will be patella tendon or hamstrings tendon depending on the surgeon's preference. All other care will be routine, including immediate post-operative care.", 'armGroupLabels': ['ACL Reconstruction Group'], 'otherNames': ['ACL Reconstruction', 'ACLR', 'ACL surgery', 'Anterior Cruciate Ligament Surgery', 'Surgical Management']}

Primary Outcomes:
- {'measure': 'Knee Injury and Osteoarthritis Outcome Score (KOOS4)', 'description': 'The score is derived from 4 of 5 subscales; pain, symptoms, difficulty in sports and recreational activities, knee related quality of life.', 'timeFrame': '18 months post randomisation'}

Please estimate the sample size based on the assumption: 
90% power at a two-sided 5% significance level, intra-cluster correlation (ICC) of 0.06, cluster size mean (SD) of 26, 5 (12) for ACL reconstruction and 43, 3 (5) for rehabilitation groups, and just over 15% missing data.
Sample size
        
          The number of participants
          In total, 320 participants will be recruited to the study. The minimal clinically important change (MIC) for the KOOS score is 8â10 points [36]. Estimates of the minimal detectable change (MDC) for the two KOOS subscales most relevant for ACLD vary between five and 12 points (Symptoms 5â9, and Sport/Rec 6â12) [36]. A mean target difference of eight points in the primary outcome, KOOS4, along with a standard deviation of 19 (the highest value observed in a trial of acute patients at baseline amongst the KOOS subscales) were assumed [37, 38]. Given these assumptions, 120 participants per group are required (1:1 allocation, 240 in total) to achieve 90% power at two-sided 5% significance level in the absence of any clustering of outcome. However, to ensure sufficient power, clustering (clsampsi Stata command [39]) has been allowed for by conservatively assuming an intra-cluster correlation (ICC) of 0.06 [40] and cluster size n, mean (SD) of 26, 5 (12) and 43, 3 (5) for the ACL reconstruction and rehabilitation groups, respectively. This leads to the larger number of 130 participants per group (260), which has just over 80% power. Given the conservative nature of the assumed values and the anticipated gain in precision from adjusting for the baseline scores and other randomisation factors, actual power is likely to be higher even in the presence of clustering. To allow for just over 15% missing data (response in a similar trial [26]), 320 participants will be needed.
          An interim analysis will be carried out to estimate the magnitude of clustering for the 6âmonths KOOS4 outcome once data is available for 100 participants. Based upon this, a decision as to whether the sample size should be increased to allow for a greater level of clustering than anticipated will be made.