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The Bone & Joint Journal
Vol. 100-B, Issue 7 | Pages 862 - 866
1 Jul 2018
Darrith B Bell JA Culvern C Della Valle CJ

Aims

Accurate placement of the acetabular component is essential in total hip arthroplasty (THA). The purpose of this study was to determine if the ability to achieve inclination of the acetabular component within the ‘safe-zone’ of 30° to 50° could be improved with the use of an inclinometer.

Patients and Methods

We reviewed 167 primary THAs performed by a single surgeon over a period of 14 months. Procedures were performed at two institutions: an inpatient hospital, where an inclinometer was used (inclinometer group); and an ambulatory centre, where an inclinometer was not used as it could not be adequately sterilized (control group). We excluded 47 patients with a body mass index (BMI) of > 40 kg/m2, age of > 68 years, or a surgical indication other than osteoarthritis whose treatment could not be undertaken in the ambulatory centre. There were thus 120 patients in the study, 68 in the inclinometer group and 52 in the control group. The inclination angles of the acetabular component were measured from de-identified plain radiographs by two blinded investigators who were not involved in the surgery. The effect of the use of the inclinometer on the inclination angle was determined using multivariate regression analysis.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_II | Pages 218 - 219
1 Jul 2008
Bell JA Stigant M
Full Access

Background: Researchers have measured exposure to sitting using self-reported questionnaires and observational analysis. Such methods are not a reliable measure of daily exposure or sensitive enough to take into account lumbar posture when seated. Recent innovations have produced a fibre-optic goniometer (FOG) that can continuously measure sagittal lumbar posture, although this single sensor is unable to identify if the user is sitting, standing or walking.

Methods: A new system was developed utilising a second FOG attached to the hip. Movement characteristics of the hip and lumbar spine were described and used to develop software to predict activity (sitting, standing, walking). Subsequently 10 participants were asked to wear the FOGs for 8 minutes whilst their behaviour was recorded using a video camera. MPEG video sequences were produced and each activity was coded at a point in time and compared against the 2 FOG software model.

Results: All Participants found the system comfortable to wear. Validation of the software against the MPEG files showed high sensitivity for sitting (90%), standing (98%), and walking (95%). Positive predictive value was high for sitting (93%), standing (89%) and walking (94%). The overall agreement between video analysis and the FOG software was 92%

Conclusions: Developing the FOG has produced a practical system capable of continuously measuring sedentary workers basic activity in terms of sitting standing and walking. This novel tool will now be used in a prospective study of sedentary workers to determine the influence of seated lumbar posture on the development of LBP.