Acoustic analysis to monitor implant seating and early detect fractures in cementless THA: An in vivo study

Abstract

The initial stability of cementless total hip arthroplasty (THA) implants is obtained by an interference fit that allows osseointegration for a long term secondary stability of the implant. Yet, finding the insertion endpoint that corresponds to an appropriate initial stability is currently often based on a number of subjective experiences of the orthopedic surgeon, which can be challenging. In order to assist the orthopedic surgeons in their pursuit to find this optimal initial stability, this study aims to determine whether the analysis of sound that results from the implant insertion hammer blows can be used to objectively monitor the insertion process of cementless THA implants. An in vivo study was conducted. The experimental results revealed vibro‐acoustic behavior sensitive to implant seating, related to the low frequency content of the response spectra. This sensitive low‐frequency behavior was quantified by a set of specific vibro‐acoustic features and metrics that reflected the power and similarity of the low‐frequency response. These features and metrics allowed monitoring the implant seating and their convergence agreed well with the endpoint of insertion as determined by the orthopedic surgeon. Intraoperative fractures caused an abrupt and opposite change of the vibro‐acoustic behavior prior to the notification of the fracture by the orthopedic surgeon. The observation of such an abrupt change in the vibro‐acoustic behavior can be an important early warning for loss of implant stability. The presented vibro‐acoustic measurement method shows potential to serve as a decision supporting source of information as it showed to reflect the implant seating.

Using Acoustic Vibrations as a Method for Implant Insertion Assessment in Total Hip Arthroplasty

“…The variance in data distribution may be caused by the variation in PU foam-filled core of the wooden bone model. In both the in vitro and in situ study, the contact microphone recorded a remarkably low amount of ambient noise (e.g., talking, instruments/equipment bumping into each other) in relation to the hammer blow, shown as gaps in Figure 2c, also compared to, for example, ambient audio recording [19], which suggests that it can be a useful tool in the OR and not just limited to recording THA acoustic emissions. In all studies, the frequency peaks are clearly visible and can be isolated to analyze, for example, the peak energy.…”

“…Shibunama et al [14] used a contact microphone on the bone itself (n = 1) to pick up less ambient noise and suggested that their system can help determine the right stem size. Other similar arthroplasties involving acoustic analysis have been carried out recently in an in vitro femur setup [15,16], acetabulum setup (with force sensors) [17], (with non-contact audio microphone) [18], in silico femur setup [16] and in vivo [19].…”

Development of an Instrument to Assess the Stability of Cementless Femoral Implants Using Vibration Analysis During Total Hip Arthroplasty

“…A surgeon’s ability to consistently ensure optimal initial intraoperative implant stability for his or her patients is crucial to assure satisfactory long-term fixation of primary and revision femoral implants in cementless total hip arthroplasty (THA) [1] . Previous research [2] – [6] has shown that vibration methods are sensitive to changes that occur between bone and implant when contact is established during the insertion of the implant into the bone. These non-destructive vibration techniques have their origin in civil engineering where they are referred to as Structural Health Monitoring (SHM) techniques [7] .…”

“…Most comprise a mechanism to attach the instrument to the implant (‘connector’) and a part on which actuation and acquisition can be performed (‘subsystem’). Goossens et al [5] investigated the sound that resulted from insertion hammer blows to monitor femoral implant seating. This article presents an alternative approach in which a non-destructive vibration excitation was applied to the system in between insertion hammer blows, while contact-based sensors captured the response.…”

“…This article presents an alternative approach in which a non-destructive vibration excitation was applied to the system in between insertion hammer blows, while contact-based sensors captured the response. The advantages of this approach over [5] are that it is repeatable and less affected by ambient airborne noise and operator variability. The first part of this study investigates the requirements for such an instrument and uses them to propose a proper shape for a femoral SHM instrument.…”