First-line treatment for femoroacetabular impingement syndrome and hip-related quality of life: study protocol for a multicentre randomised controlled trial comparing a 6-month supervised strength exercise intervention to usual care (the Better Hip Trial)

Background and rationale

The overall incidence rate of femoroacetabular impingement syndrome (FAIS) is 54 per 100 000 person-years, primarily affecting physically active young-aged to middle-aged adults.1 FAIS is defined as a motion-related and position-related clinical condition of the hip with a triad of symptoms, clinical signs and radiographic findings.2 The radiographic findings include cam, pincer or mixed morphology, and these morphological changes, especially cam, may lead to labral and cartilage lesions, and subsequently early hip osteoarthritis.1–8 Furthermore, it is increasingly recognised that FAIS might account for previously undiagnosed hip pain in young adults.5 9 Patients with FAIS usually present with hip pain, limiting activities of daily living, sports participation and hip-related quality of life (QoL).2 10

In addition, patients with FAIS have decreased maximal muscle strength in all main hip movements compared with asymptomatic controls.11 Previous cross-sectional,12 current state of knowledge papers,13 interventional cohort,14 and randomised controlled trial (RCT)15 studies found that higher maximal muscle strength in patients with FAIS is associated with less pain, improved hip function, and better QoL.12–15

There is a consensus that first-line treatment in most patients should be non-surgical.16 Since a proportion of patients seem to respond positively to physiotherapy, including pain medication, patient education, activity modification and strengthening exercises, a physiotherapy intervention is recommended before considering surgery.2 14 17 Several RCTs have investigated the effectiveness of non-surgical treatment compared with surgical treatment.18–23 All RCTs included a multicomponent and individualised treatment approach as recommended. It is, therefore, not clear which of the different non-pharmacological programme components were effective. Importantly, most of the evaluated programmes included strengthening exercises, but it is not clear if the existing recommendations on designing strength training programmes were followed for key programming variables such as exercise modality,19 20 frequency,20 duration19 or dose18 (ie, intensity and volume).24 25 Moreover, obtaining a sufficient stimulus is critical to induce optimal muscular and neural adaptations and subsequently optimal muscle strength gains following strength training.25 26

The muscle strength profile of the hip (ie, flexion, extension, abduction, adduction, internal rotation and external rotation strength) of FAIS patients showing general deficits when compared with hip-healthy people offers further support for the inclusion of strengthening exercises when designing a non-surgical first-line treatment intervention for these patients. Accordingly, a randomised feasibility study suggests that strengthening exercises compared with stretching exercises may improve pain, function and QoL above the minimal clinical important difference in patients with FAIS.15 27 Also in support, preliminary data from a feasibility study similarly showed that strengthening exercises in patients with FAIS are safe, feasible and appear to moderately improve function and maximal muscle strength.28 Interventions evaluating strength training programmes based on existing recommendations are highly warranted in persons with FAIS.

Usual care for patients diagnosed with FAIS in Denmark includes advice to undertake hip exercises for at least 3 months before considering surgery, but there is currently very little evidence to support a specific exercise intervention as first-line treatment.29 Consequently, high-quality evidence on the effects of applying strengthening exercises for patients with FAIS is highly warranted to guide and optimise future exercise interventions when prescribing first-line treatment in persons with FAIS.16 This is further supported by an international panel of clinicians and researchers who recently rated research priorities in hip conditions affecting younger people and stated that RCTs investigating best physiotherapy practices in patients with FAIS are a priority.16

Objectives

Therefore, we will conduct an RCT investigating the clinical effectiveness and cost-effectiveness of a supervised strength exercise intervention compared with usual care as first-line treatment in patients with FAIS. Furthermore, in a secondary explanatory analysis, we will explore how exercise adherence and the volume of a supervised strength exercise intervention mediate outcomes.

We hypothesised that (1) 6 months of supervised strength exercise intervention is superior (ie, ≥6 points difference on the International Hip and Outcome Tool 33, iHOT-33), to usual care in improving hip-related QoL in patients with FAIS after a 6-month intervention, (2) 6 months of supervised strength exercise intervention is cost-effective compared with usual first-line care at 12-month follow-up in patients with FAIS and (3) high exercise session adherence (ie, the number of training session attended expressed as a % of the total number of prescribed sessions) and volume (eg, sets multiplied by the number of repetitions per set summarised across all attended sessions and exercises) will be superior to low exercise adherence and volume in mediating objectively and patient-reported outcome measures in patients with FAIS.