An Investigation into the Dynamic Loading of Ceramic-on-Ceramic Total Hip Replacements and its Relevance to Squeaking

Transcription

1 An Investigation into the Dynamic Loading of Ceramic-on-Ceramic Total Hip Replacements and its Relevance to Squeaking Jim W. Pierrepont, MEng 1, Andrew J. Shimmin, MBBS, FRACS 2, Jonathan V. Baré, MBBS, FRACS 2, Hans Feyen 2, Brad P. Miles, PhD 3. 1 University of Sydney, Sydney, Australia, 2 Melbourne Orthopaedic Group, Melbourne, Australia, 3 Optimized Ortho, Sydney, Australia. Disclosures: J.W. Pierrepont: 3B; Optimized Ortho Pty Ltd. 5; Optimized Ortho Pty Ltd. A.J. Shimmin: 2; CeramTec GmbH. 3B; Corin Group PLC, MatOrtho Ltd. 3C; Optimized Ortho Pty Ltd. 5; Optimized Ortho Pty Ltd. J.V. Baré: 3C; Optimized Ortho Pty Ltd. 5; DePuy Orthopaedics. H. Feyen: None. B.P. Miles: 2; Waldemar Link GmbH & Co. 3B; Optimized Ortho Pty Ltd. 4; Optimized Ortho Pty Ltd. Introduction: Squeaking rates in ceramic-on-ceramic hips have been reported to vary between % (Keurentjes 2008, Walter 2008, Jarrett 2009). In vitro studies have shown that a complex chain of events are required to generate a reproducible squeak, initiated by the formation of a wear stripe on the head, generated during an edge-loading event. Once the magnitude of the hip joint reaction force reaches a critical limit and is centred through the head wear scar, reproducible squeaking can be heard, even in well lubricated conditions (Sanders 2012). Theoretically therefore, if the initial edge-loading event can be avoided, squeaking rates should decrease. The aim of this study was to investigate the incidence of edge-loading in squeaking and matched controlled silent ceramic hips, using a musculoskeletal modelling technique that simulates the patient performing functional activities. Methods: Eighteen patients with reproducible squeaking in their Delta Motion ceramic bearings (Depuy, Warsaw, IN) were analysed using the Postoperative Kinematic Simulation Software (Optimized Ortho, Sydney). All hips squeaked during a flexion activity. The software uses standard medical imaging to produce a patient-specific simulation of the patient performing two functional activities; rising from a chair and stepping-up with the contralateral leg. The software calculates the magnitude and direction of the dynamic force at the hip and traces the contact area between prosthetic head/liner across the articulating surface, Fig 1. The incidence of edge-loading can then be determined based on the location of the contact patch in relation to the true edge of the acetabular liner, Fig 2. A control group of thirty-six silent hips were recruited and matched for implant, component orientation, range of motion, beighton score and BMI. These patients were also analysed with the Postoperative Kinematic Simulation Software. Results: The squeaking group had a larger sagittal pelvic ROM from stand-to-sit than the control group, 14.4 and 6.3 respectively (p = 0.01), Fig 3. The cup anteversion when seated was significantly less in the squeaking group than the control group, 8.1 and 21.1 respectively (p < 0.001). The Contact Patch Edge to Rim (CPER) distance was significantly less in the squeaking group than the control group, -2.8mm and 2.6mm respectively, (p < 0.001). A negative CPER value signifies the contact patch passing over the edge of the liner. Discussion: The Postoperative Kinematic Simulation Software showed significantly more edge-loading in the squeaking group than the control group. The squeaking group had a larger range of motion of the pelvis in the sagittal plane than the silent hips. The larger pelvic ROM caused more anterior pelvic tilt at the time of seat-off, therefore reducing the functional anteversion of the cup and exposing the posterior aspect of the liner to edge-loading. Acetabular components orientated in currently recognised safe-zones can still edge-load and squeak, likely due to the dynamic behaviour of the pelvis during functional activities. Sagittal pelvic rotations during activities of daily living can have a substantial effect on the functional anteversion of the acetabular component. Understanding patient-specific kinematics and orientating the components accordingly, could help reduce the squeaking rates in ceramic-on-ceramic bearings. Simple static analyses might not be sufficient when evaluating problems associated with cup orientation. Significance: Static analyses of total joint replacement might not be sufficient when evaluating problems associated with component orientation. If easily accessible dynamic modelling techniques can be used to pre-operatively define a patientspecific component orientation, the problems associated with implant malorientation could be reduced. Acknowledgments: Supported by Optimized Ortho, Sydney References: 1.Keurentjes JC, Kuipers RM, Wever DJ, Schreurs BW. High incidence of squeaking in THAs with alumina ceramic-onceramic bearings. Clin Orthop Relat Res 2008;466: Walter WL, Waters TS, Gillies M, et al. Squeaking hips. J Bone Joint Surg [Am] 2008;90-A(Suppl): Jarrett CA, Ranawat AS, Bruzzone M, et al. The squeaking hip: a phenomenon of ceramic-on-ceramic total hip arthroplasty. J Bone Joint Surg [Am] 2009;91-A: Sanders A, Tibbitts I, Brannon R. Concomitant evolution of wear and squeaking in dual-severity, lubricated wear testing of

2 ceramic-on-ceramic hip prostheses. J Orthop Res Sep;30(9):

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4 ORS 2014 Annual Meeting Poster No: 0868

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