Acoustic characteristics of broaching procedure for post-operative stem subsidence in cementless total hip arthroplasty

Purpose Avoiding stem subsidence is crucial for achieving better outcome for cementless total hip arthroplasty (THA). The aim of this study was to develop a prediction model for the incidence of post-operative stem subsidence using full quantitative acoustic parameters in hammering sound during the broaching procedure and to assess the accuracy of this prediction model. Methods The acoustic parameters of the hammering sounds during a broaching procedure for 55 hips in 49 patients who underwent THAs with cementless taper-wedged stem were analysed. The stem subsidence was assessed at one month post-operatively, and the relationship between the acoustic parameters and the value of stem subsidence was investigated. Results The average stem subsidence was 2.15 +/- 2.91 mm. The subsidence 3 mm or more was observed in eleven hips (20%), and 5 mm or more was observed in seven hips (12.7%). Basic patient's characteristics, preoperative femoral morphology and immediate post-operative canal fill ratio and stem alignment were not significantly related to the volume of stem subsidence. Nine acoustic parameters were significantly correlated with the value of subsidence. The prediction model for post-operative subsidence using only acoustic parameters during broaching procedure was established, and this model showed a positive prediction value of 100% and a negative prediction value of 90.6% for post-operative stem subsidence at 5 mm or more. Conclusion Post-operative stem subsidence can be predicted by using acoustic parameters of the hammering sound during the broaching procedure. Our results suggest that we are at the start of a new era in which novel and innovative smart technologies can be used to assist in orthopaedic surgery.