The objective of this study is to investigate the feasibility of functional 3D biomechanical assessment and EMG analysis of gait and a sit to stand tasks in the immediate post-operative phase following total hip arthroplasty.

Functional recovery is often an important priority for patients undergoing total hip arthroplasty (THA) and it is thought that abnormal biomechanics may be an obstacle to full recovery of physical function. While there has been extensive research on the biomechanics of gait and other activities of daily living following THA, the earliest reported post-operative assessment of function using 3D motion analysis for kinematics and kinetics has been at 6 weeks post-surgery. There is a paucity of data from the immediate post-operative phase prior to patient discharge from hospital.

In recent years there has been an increase in initiatives such as fast-track or enhanced post-operative recovery programs following joint arthroplasty, with the aim being an early return to function and shorter hospital length of stay whilst maintaining the low morbidity and mortality and high satisfaction rates typically associated with THA. There has also been continued research and developments on improving the THA procedure and while initial focus on improving THA surgery centred on implant design, materials and fixation to bone, there has been increased attention to surgical approach. In the last 10 years the use of minimally invasive surgical techniques has become more widespread due to the potential reported benefits. These include a shorter incision length, reduced muscle damage, reduced pain and less bleeding. When combined, these benefits may lead to reduced length of hospital stay and earlier return to function.

With so much focus centred on early return to function, there is a need to objectively measure function in the immediate post-operative phase. This would allow us to evaluate the effect of minimally invasive surgical approaches and enhanced recovery programs, which are primarily centred on early recovery from surgery. The use of 3D motion capture technology allows for accurate assessment of joint movement in three planes during dynamic movements and has been used extensively in the evaluation of function in patients with significant hip pathology before and after total hip arthroplasty. As aforementioned, to date the earliest post-operative motion analysis has been at 6 weeks after THA. Similarly, the earliest reported time point for muscle activation analysis using EMG is 6 weeks post THA. The aim of this study is assess the feasibility of 3D motion analysis including EMG in the immediate post-operative phase following THA in a hospital which incorporates an Enhanced Recovery After Surgery (ERAS) program as part of routine clinical care. This pilot project will guide development of future protocols which require early post-operative 3D biomechanical analysis.

For the purposes of this study the investigators define the immediate post-operative time point as the day the patient is discharged from the inpatient rehabilitation team and therefore deemed "safe" to mobilise independently by the ward physiotherapists.

Subject recruitment and retention will be closely monitored throughout the trial, allowing us to measure recruitment and dropout rates. Where possible, reasons for declining participation in the study and reasons for dropout will be documented. The ability of the patients to perform study related assessments will be recorded in addition to the reason for them being unable to perform the task, this will be done via a questionnaire that patients will complete at the end of each 3D biomechanical assessment session.

Patients will be asked to attend a biomechanical testing session before their surgery. After surgery they will follow standard aftercare, and on the day of discharge from the inpatient physiotherapy team they will be asked to attend the second biomechanical testing session. The third and fourth sessions will be on day three and day seven post-surgery, and the final session will take place when they return to the hospital for their standard three month follow up with the arthroplasty team. At the end of the three month visit, their involvement in the study will be complete.

Biomechanical movement analysis will be carried out in an on-site movement analysis laboratory. Study participants will be required to wear suitable clothing (e.g. tee shirt and shorts) and be barefoot. A number of reflective markers and surface electrodes will be attached to specific locations on the body using suitable double sided tape which can be tracked by a number of infrared cameras. participants will be asked to perform the following tasks; walking, sit-to-stand and stand-to-sit. Each task will be performed at least three times to enable the collection of three good sets of data. A motion capture system will collect limb and torso movements during the task performances while force plates will collect ground reaction forces.

Inclusion Criteria:

• Patients suitable for posterolateral approach total hip arthroplasty
• Able to give informed consentAble to return to study site for follow-up
• BMI under 35

Exclusion Criteria:

• Previous hip procedure in the previous twelve months
• Previous knee surgery other than arthroscopy and medial menisectomy in the last twelve months
• Symptomatic foot, knee, contralateral hip or spinal pathology
• Any medical condition limiting normal ambulation e.g. stroke, Parkinsons disease, severe lymphedema, advanced cardiac disease
• Unable to read and understand English and follow verbal and visual instructions unless they can bring a relative or friend to all study assessments to act as a translator

Patients who have been referred to the Golden Jubilee National Hospital for total hip replacement.