UNICOMPARTMENTAL KNEE ARTHROPLASTY PATIENTS WALK FURTHER AND LIVE LONGER: WRIST-WORN ACCELEROMETRY DATA MAY EXPLAIN THE PROTECTIVE EFFECT OF PARTIAL KNEE ARTHROPLASTY AT TEN YEARS POSTOPERATIVELY

Introduction Implant registries report a higher ‘failure’ rate for the partial in comparison to the total approach to the knee, while also recording a lower mortality. The use of wearable devices to report on physical activity has enabled a strong link to be established between exercise and health. We surmised that the higher levels of activity seen following partial replacement may be associated with lower mortality rates in the longer term. Materials and Methods The UK biobank involved half a million people who were recruited between 2006 and 2010. Of these, 104,000 used a wrist worn accelerometer (Axivity AX3) for 7 consecutive days between 2013 and 2015. This data was linked to hospital episode statistics and death registries. Patients were identified who had undergone partial or total knee arthroplasty prior to the use of the accelerometer. The data was analysed using an algorithm which detects walking periods, estimated step counts and physical activity. Results 631 people had undergone TKA, while 134 had undergone UKA. When measured around 3 years following sugery, UKA took on average 9021 steps, while TKA took 7747 steps. At 10 years following surgery, 4/130 (3%) UKA patients had died, while 36/596(6%) TKA patients had died. Activity metrics were strongly linked to mortality from 10 years onwards, eg daily step count (HR 0.92 per thousand steps. These associations persisted after adjustment for age, sex, BMI, comorbidity, smoking, procedure type. Conclusions Pervasive monitoring data from a large observational cohort study reports a substantially higher level of activity following partial replacement. This may explain the reduction in deaths observed at 10 years following surgery.