Introduction

Following primary total knee arthroplasty (TKA), patients experience pain relief and report improved physical function and activity. However, there is paucity of evidence that patients are truly more active in daily life after TKA. The aims of this study were: 1) to prospectively measure physical activity with a wearable motion sensor before and after TKA; 2) to compare patient-reported levels of physical activity with objectively assessed levels of physical activity before and after TKA; 3) to investigate whether differences in physical activity after TKA are related to levels of physical function.

Accelerometer based gait analysis (AGA) is a potential alternative to the more commonly used skin marker based optical motion analysis system(OMAS). The use of gyroscopes in conjunction with accelerometers (i.e. inertial sensors), enables the assessment of position and angular movements of body segments and provides ambulatory kinematic characterisation of gait.

We investigated commonly used gait parameters and also a novel parameter, Pelvic obliquity (PO) and whether they can be used as a parameter of physical function and correlate with classic clinical outcome scores

Gait was studied in healthy subjects (n=20), in patients with end stage hip OA (n=20) and in patients with end stage knee OA (n=20). Subjects walked 20 metres in an indoor environment along a straight flat corridor at their own preferred speed. A 3D inertial sensor was positioned centrally between the posterior superior iliac spines (PSIS) overlying S1.

Comparing gait parameters of end stage hip OA patients with an age and gender matched healthy control group, significantly lower walking speed, longer step duration and shorter step length was observed. After correcting for walking speed between groups, significantly less average range of motion of PO (RoM_po) was observed for patients with end stage hip OA compared to healthy subjects and patients with end stage knee OA.

IGA allows objective assessment of physical function for everyday clinical practice and allows assessment of functional parameters beyond time only. IGA measures another dimension of physical function and could be used supplementary to monitor recovery of OA patients after TJR.

Introduction

In orthopaedics, clinical outcome assessment (COA) is still mostly performed by questionnaires which suffer from subjectivity, a ceiling effect and pain dominance. Real life activity monitoring (AM) holds the promise to become the new standard in COA with small light weight and easy to use accelerometers. More and more activities can be identified by algorithms based on accelerometry. The identification of stair climbing for instance is important to assess the participation of patients in normal life after an orthopaedic procedure. In this study we validated a custom made algorithm to distinguish normal gait, ascending and descending stairs on a step by step basis.

Introduction

Our classic outcome scores increasingly fail to distinguish interventions or to reflect rising patient demands. Scores are subjective, have a low ceiling and score pain rather than function. Objective functional assessment tools for routine clinical use are required. This study validates inertial sensor motion analysis (IMA) by differentiating patients with knee versus hip osteoarthritis in a block-step test.