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Table 1 Statistical analysis plan summary

From: Femoroacetabular Impingement Randomised controlled Trial (FIRST) - a multi-centre randomized controlled trial comparing arthroscopic lavage and arthroscopic osteochondroplasty on patient important outcomes and quality of life in the treatment of young adult (18–50 years) femoroacetabular impingement: a statistical analysis plan

Objective Outcome Hypothesis Method of analysisa
Name Type
Primary objective
 To compare pain levels at 1 year Pain (VAS) Continuous Osteochondroplasty will reduce pain compared to lavage Multiple linear regression
Secondary objectives 1
 To compare patient-reported health-related quality of life Hip function (HOS) Continuous Osteochondroplasty will improve health-related quality of life, function, and utility compared to lavage Multiple linear regression
Hip-specific disease on hip function (iHOT-12) Continuous
Physical health (SF-12 PCS) Continuous
Mental health (SF-12 MCS) Continuous
Health Utility (EQ-5D) Continuous
Secondary objective 2
 To compare hip complications Hip-related complications (e.g. re-operation) Binary Osteochondroplasty will reduce rate of re-operations compared to lavage Multiple logistic regression
Subgroup analysis
 Hip impingement severity: mild (alpha angle < 60 – > 50 degrees), moderate (alpha angle > 60 – < 83°), severe (alpha angle > 83°) Pain (VAS) Continuous Patients with severe impingement at baseline will have the greatest improvement with the osteochondroplasty procedure compared with those with moderate to mild impingement Multiple linear regression
 Gender: male, female Pain (VAS) Continuous The osteochondroplasty procedure will perform better in males Multiple linear regression
 Cartilage status (based on Tonnis and Heinecke classification): grades 3 and 4, grades 1 and 2 Pain (VAS) Continuous Osteochondroplasty will perform worse in patients with worse cartilage status (i.e. grades 3 and 4) Multiple linear regression
 Treatment of the labrum: labral repair, resection Pain (VAS) Continuous Patients receiving a labral repair will perform better than those receiving a resection as part of the osteochondroplasty procedure Multiple linear regression
Sensitivity analysis
 Trial site (centre-effects) Pain (VAS) Continuous We do not expect the effect to change substantially when centre-effects are removed from the primary analysis Multiple linear regression with centre-effects removed
 Missing data effect Pain (VAS) Continuous We do not expect the effect to change substantially without imputation for missing data Multiple linear regression with complete cases only
 Potential baseline imbalance Pain (VAS) Continuous Results will remain robust after adjusting for potential baseline imbalance on age, any comorbidities, onset of symptoms, and presence of labral tears at initial surgery Multiple linear regression with complete cases only
  1. *All regression analyses will be controlled for centre as a stratification variableVAS: Visual Analogue Scale, SF: Short Form, PCS: Physical Component Summary, MCS: Mental Component Summary, HOS:Hip Outcome Score, iHOT: International Hip Outcome Tool, EQ-5D: Euroqol-5 Dimensions