A Novel Sensor Concept for Optimization of Loosening Diagnostics in Total Hip Replacement

Abstract

The main reason for the revision of total hip replacements is aseptic loosening, caused by stress shielding and wear particle induced osteolysis. In order to detect an implant loosening early, the osseointegration of endoprosthetic implants must be measured exactly. Currently applied diagnostic methods, such as standard radiographs and clinical symptomatology, often result in an imprecise diagnosis. A novel radiation-free method to improve the diagnostic investigation of implant loosening is presented. The osseointegration of an implant can be identified using mechanical magnetic sensors (oscillators), which impinge on small membranes inside an implant component, e.g., the femoral hip stem. The maximum velocity after impingement of the oscillator depends on the osseointegration of the implant. Excitation of the oscillator is realized by a coil outside the human body. Another external coil is used to detect the velocity of the oscillator. To demonstrate the principle of the novel loosening sensor, an overdimensioned test device was designed to measure simulated loosening phases in the first experimental tests with different material layers. The overdimensioned test device of the loosening sensor showed significant differences in the various phases of fixation. Analysis of the membrane without any material layer in the case of advanced loosening resulted in a 23% higher maximum velocity compared to an attached artificial bone layer. Based on these preliminary results, the sensor system shows potential for the detection of implant loosening. Moreover, the proposed system could be used in experimental applications to determine the quality of bioactive coatings and new implant materials.

Development of a non-invasive diagnostic technique for acetabular component loosening in total hip replacements

“…Most THR stability assessment studies have focused on the femoral component [20][21][22][23][24][35][36][37][38][39][40][41][42]. Vibration analysis studies on acetabular loosening are limited because the acetabulum has a complex geometry compared to the femur and has a thicker overlaying soft tissue layer, which acts as a signal buffer.…”

“…Georgiou and Cunningham [23] also compared vibration analysis with standard radiological assessment and demonstrated that vibration analysis improved diagnostic precision by 20%; moreover, they were able to detect 13% more cases than radiological diagnosis with 81% sensitivity and 89% specificity. Other research groups have used vibration analysis for different orthopaedic applications such as; the telemetry technique to assess THR femoral loosening [24][25][26], trans-femoral osseointegration [27][28][29], intra-operative initial implant stability [6,[30][31][32][33], THR femoral stability utilising acoustic resonance responses [7,[34][35][36][37][38][39][40][41], and complete THR component loosening (femoral and acetabular) [5].…”

“…The majority of previous studies on vibration analysis [20][21][22][23][24][35][36][37][38][39][40][41][42] assessed loosening of the femoral stem. Since a high rate of loosening in the acetabular component has been reported in the clinically [43]; therefore, the aim of the present study was to compare ultrasound and accelerometer methods and to examine the viability of the vibration analysis technique to accurately detect acetabular component loosening.…”

Loosening detection of the femoral component of hip prostheses with extracorporeal shockwaves: A pilot study

“…The mentioned studies used either an impact hammer or an electro-magnetic shaker without one method gaining unreserved approval [19]. Only one research group worked on an alternative approach combining excitation and measurement [20,21]. They aimed for an actuator-sensory-element, which is intended to be implemented into the prosthesis itself.…”

Piezoresistive sensors for force mapping of hip-prostheses

“…Information concerning mechanical stress of bone cement and hip-joint small dislocations monitoring are fundamental to promote high durability of the prosthesis, comfort and reliability to the patient. In this sense strong efforts are being done in order to develop sensors for the measurement of cement-prostheses interface forces based on different transducers and geometries [5][6][7][8][9][10], but the issue is far from being solved for practical situations.…”