Short summary

Hip osteoarthritis is associated with pain, physical dysfunction, and poor health status, and is increasingly treated with total hip arthroplasty. Exercise is recommended in national and international guidelines for hip osteoarthritis and progressive resistance training has shown clinically relevant improvements in activities of daily living function. To date, no randomised controlled trials have investigated the effect of total hip arthroplasty in comparison to non-surgical treatment.

Rationale

Hip osteoarthritis (OA) is a common musculoskeletal disorder associated with joint pain, dysfunction of activities of daily living (ADL), decreased muscle strength, and decline in health-related quality of life status. The prevalence of hip osteoarthritis has been estimated to be 11% in the general adult population, increasing with age and risk factors include obesity and reduced physical activity.

Total hip arthroplasty (THA) has been described as the operation of the century, resulting in reduced pain, correction of joint alignment, improved physical function, and high satisfaction in patients with hip osteoarthritis. In Denmark, approximately 10.400 primary THA surgeries are performed annually, and the yearly incidence rate of this procedure has increased dramatically from 80 to 180 per 100.000 persons between 1995 and 2016. However, patients may never recover full physical function and muscle strength after surgery.

Exercise has been shown to improve physical function and reduce pain in patients with hip OA, and is recommended as a treatment modality in national and international clinical guidelines. Several different exercise modalities have been investigated including aerobic, neuromuscular, and resistance training programs. Nevertheless, the current evidence is inconclusive in relation to optimal exercise content and intensity. 

Progressive resistance training (PRT) performed with a high-velocity concentric phase (explosive type) has been reported to increase muscle power compared to conventional PRT training using a slow-to-moderate velocity, which is considered important for improving ADL function in healthy older adults.  In patients with end-stage hip OA,  PRT is considered to be safe and feasible, and a recent randomised controlled trial displayed clinically relevant improvements in ADL and muscle function after 10-weeks of supervised explosive-type PRT in patients with end-stage hip OA scheduled for THA compared to standard preoperative care.

The effect of exercise combined with a low number of adverse events may have an impact on patient motivation for postponing or eliminating surgery. Moreover, a recent high-quality randomised controlled trial evaluating the additive effect of total knee arthroplasty surgery in patients with knee osteoarthritis, showed that total knee arthroplasty followed by non-surgical treatment (i.e. neuromuscular exercise, education, dietary advice, use of insoles, and pain medication) resulted in greater pain relief and functional improvement compared to non-surgical treatment alone. However, 68% of the patients assigned to the non-surgical treatment group, did not undergo total knee arthroplasty after two-years of follow-up. 

To date, no studies have investigated the effect of THA followed by standard postoperative care compared to supervised explosive-type PRT in patients with end-stage hip osteoarthritis. This comparison is of upmost importance because it is unknown whether non-surgical treatment may be used as an alternate to surgery.

Therefore, the aim is to investigate whether THA followed by standard care is superior to a 12-week non-surgical supervised explosive-type PRT programme for improving patient-reported hip function and pain 6 months after initiating the treatment, measured using the Oxford Hip Score (OHS), in patients with end-stage hip OA eligible for THA.

Description of the cohort

Patients fulfilling the following inclusion and exclusion criteria will be invited to participate in the trial.

Inclusion criteria:

1. Adults aged 50 years or above.

 2. Clinical history and symptoms consistent with primary hip OA (including hip OA due to mild hip dysplasia that may be treated with standard components) and radiographic verified hip OA defined as joint space narrowing <2 mm.

 3. Considered eligible for THA by an orthopaedic surgeon (i.e. duration of symptoms >3 months, hip related pain, functional impairment or decreased range of motion (ROM), and attempted treatment with analgesics).

Exclusion criteria:

1. Severe walking deficits (dependency of two crutches or walker). 

2. Body Mass Index >35 kg/m2.

3. Lower extremity fractures within one-year prior to inclusion.

4. Planned other lower extremity surgery within six months.

5. Cancer diagnosis and receiving chemo-, immuno- or radiotherapy.

6. Neurological diseases (e.g. previous stroke, multiple sclerosis, Parkinson's, Alzheimer's).

7. Other reasons for exclusion (i.e. inadequacy in written and spoken Danish, mentally unable to participate, etc.).

Data and biological material

The primary outcome measure will be the between-group difference in change from baseline to 6 months follow-up in the Oxford Hip Score (OHS). 

Key secondary outcomes measures comprise the Hip disability and Osteoarthritis Outcome Score (HOOS) subscales (pain, symptoms, activities of daily living, hip-related quality of life, and sports and recreation) University of California Los Angeles (UCLA) activity score, physical function tests (30-second chair stand test and 40m fast-paced walk test) and adverse events. 

Exploratory outcome measures include Visual Analogue Scale (VAS) Pain, EuroQoL Group 5-dimension (EQ-5D-5L), Medication use, Global perceived effect (GPE), Physical activity (tri-axial), and Isometric muscle strength (Hand-held dynamometry). 

Other measurements consist of Patient characteristics, Crossovers (PRT group), Compliance and progression (PRT group), Postoperative rehabilitation (THA group), and Other treatments during the study period.

Collaborating researchers and departments

Department of Orthopeadic Surgery, Næstved Hospital

• Henrik Morville Schrøder, PhD, MD

Department of Orthopeadic Surgery, Lillebaelt Hospital, Vejle Hospital

• Claus Varnum, PhD, MD

Musculoskeletal Statistics Unit, The Parker Institute, Bispebjerg and Frederiksberg Hospital

Department of Rheumatology, Odense University Hospital

• Professor Robin Christensen