Abstract
Introduction
Proper femoral reaming is a key factor for a successful outcome in cementless hip arthroplasty. Good quality reaming minimizes risks of intra-operative femoral fracture during reaming and prevents poor fitting of the implant which can lead to subsidance of the stem postoperativly. Determining the quality of reaming is largely a subjective skill and dependant on the surgeon's experience with no documented intraoprative method to assess it objectively.
Method
We recorded and analysed the frequencies of sound signals recorded via a bone conduction microphone during reaming of the femoral canal in a series of 28 consecutive patients undergoing uncemented total hip replacement performed by same surgeon. Hammaring sound frequencies and intensity were analysed by mean of computer software. The relationship between the patterns of the recorded reaming sound frequencies compared with surgeon judgment of the reaming quality intraoparativly and post operative x rays. All patients were followed up clinically and radiologically for 2 years after surgery to determine the integrity of the fix and to evaluate the stability of the prosthesis.
Results
There was a consistent pattern of frequency changes detected in all cases regardless of gender, age, bone density size of reamer etc. Our results showed that the resonances in the femur can be accurately recorded during canal reaming and proved that there is a definite increase in the amplitude of sound frequencies between 600 and 1000 Hz when the tension of the reamer moves from loose to tight during hammering. Adding all of the dB values between 600 to 1000 Hz for the loose tension sound and comparing this to the total for the tight tension sound showed an average of 449.6% increase. Our Analysis of the sound signals changes was comparable to the adequacy of the reaming postoperatively
Conclusion
There are identifiable audio frequency patterns changes associated with satisfactory reaming of the femoral canal. Our findings may pave the way for the development of a real-time intraoperative reaming audio analyser which can guide the surgeon to the optimal reaming tension.
