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. A small, lightweight 3D-accelerometer taped to the lateral side of the affected (patients) or non-dominant (healthy subjects) upper leg served as the activity monitor. 13 Subjects (9 patients, 4 healthy) walked a few steps before descending a flight stairs (20 steps with a 180o turn in the middle), walked some steps more, turned around and ascended the same stairs. Templates (up, down and level) were obtained by averaging and stretching the vertical acceleration in the 4 healthy subjects. Classification parameters (low pass (0.4 Hz) horizontal (front-back) acceleration and the Euclidian distance between the vertical acceleration and each template) were obtained for each step. Accuracy is given by the percentage of correctly classified steps.Introduction
Methods
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. Step up and down from a block (h=20cm, 3 repetitions) loading the affected (A) and unaffected (UA) leg was measured in n=59 subjects using a small inertial sensor (3D gyro and accelerometer, m=39g) attached onto the sacrum. Patients indicated for either primary unilateral THA (n=20; m/f=4/6, age=69.4yrs ±9.8) or TKA (n=16;m/f=7/9;age=67.8yrs ±8.2) were compared to healthy controls (n=23;m/f=13/10;age=61.7yrs ±6.2) and between each other to validate the test's capacity for diagnostics and as an outcome measure. The motion parameters derived (semi-) automatically in Matlab for both legs were: front-back (FB-) sway and left-right (LR-) sway (up and down); peak-to-peak accelerations (Acc) during step down. In addition the asymmetry between both legs (ASS) was calculated for each parameter. Group differences were tested (t-test) and the diagnostic value determined by the area under the curve (AUC) of the ROC-curve.Introduction
Methods
In orthopaedics, clinical outcome assessment (COA) is mostly performed by questionnaires which suffer from subjectivity, a ceiling effect and pain dominance. Real life activity monitoring (AM) can objectively assess function and becomes now feasible as technology has become smaller, lighter, cheaper and easier to use. In this study we validated a custom made algorithm based on accelerometry using different orthopaedic patients with the aim to use AM in orthopaedic COA. A small, lightweight 3D-accelerometer taped to the lateral side of the affected upper leg served as the activity monitor. AM algorithms were programmed in Matlab to classify standing, sitting, and walking. For validation a common protocol was used; subjects were asked to perform several tasks for 5 or 10 seconds in a fixed order. An observer noted the starting time of each task using a stopwatch. Accuracy was calculated for the number of bouts per activity as well as total time per activity. 10 Subjects were chosen with different pathologies (e.g. post total knee/hip arthroplasty, osteoarthritis) since the difference in movement dynamics in each pathology poses a challenge to the algorithm.Introduction
Methods
Large wear rate reductions have been shown for crosslinked PE in simulators and short- to mid-term clinical wear studies. However, concerns persist about long-term in-vivo oxidation (especially with annealed PE), late accelerating wear and the possibly higher osteolytic potential of crosslinked PE particle debris. This is the first long-term study comparing conventional to crosslinked PE investigating whether the wear reduction is maintained in the long-term and if reduced osteolysis becomes evident. In a prospective study 48 primary THA patients (Stryker ABG-II, 28mm CoCr heads) were randomized to either receive a first generation crosslinked PE (Stryker Duration: 3MRad gamma irradiation in N2, annealed) or then conventional, now “historic” PE (3MRad gamma irradiation in air). Both groups were statistically non-different (p>0.1) regarding age (63.9 years), gender, BMI, stem and cup size, cup inclination, liner thickness or pre- and post-op HHS leaving the insert material as the only variable. Patients were followed-up annually using the Harris Hip score, AP and lateral radiographs and digital wear measurements using Roman V1.70 [1, 2]. Wear and radiographic signs of osteolysis were analysed at a mean follow-up of 12.9 years (12.0–13.3). Groups were compared using the t-test (means) or the Fisher Exact test (proportions).Introduction
Materials & Methods
