Graphical representation of range of motion in the assessment of total hip arthroplasty : innovation report

Abstract

Total Hip Arthroplasty (THA) is a successful technique restoring lost mobility to patients suffering from osteoarthritis. A successful THA normalises the biomechanics of the hip joint so that a patient can achieve the required range of motion to fulfil their daily activities. A recent development in THA implant technologies has been the introduction of femoral neck modularity. Assessment of femoral neck modularity has been limited by two factors. Firstly, range of motion requirement is not well understood and secondly previous clinical reports have lacked a comparison against an established successful THA implant. This study has successfully addressed these limiting factors by developing an innovative range of motion benchmark which considers the activities a person is required to undertake during their daily routine. The benchmark was developed using a systematic review of the literature focussing on hip joint biomechanics. This has been the first study to provide a clinically meaningful representation of hip joint range of motion which permits operative outcome to be directly compared against an established benchmark. Integration of the range of motion benchmark within the surgical environment was achieved by using a surgical navigation measurement device. Intra-operative measurement meant that post-operative range of motion could be simulated and compared against the requirement set by the range of motion benchmark. Distinct outcome measures have been able to be developed using this comparison which has allowed the surgical process to be assessed like a manufacturing system. Using these outcome measures, it was found that femoral neck modularity has greater potential to adjust implant orientation in comparison to non-modular femoral neck implants to achieve the ideal range of motion. However, this potential is being limited due to the current modular neck options available and because of difficulty experienced by the surgeon in assessing implant orientation. These findings have been used to develop a medical device which provides guidance to the surgeon about the THA implant orientation and thus allow them to able to make the correct modular neck choice to maximise range of motion and improve the operative outcome for the patient