POLYETHYLENE LINER MOTION IN DUAL MOBILITY HIP PROSTHESES: STATIC AND DYNAMIC RADIOSTEREOMETRY IN 16 CASES ONE YEAR AFTER OPERATION

Orthopaedic Proceedings, vol. 105-B, pp. 148

Abstract

Dual mobility hip arthroplasty utilizes a freely rotating polyethylene liner to protect against dislocation. As liner motion has not been confirmed in vivo, we investigated the liner kinematics in vivo using dynamic radiostereometry. 16 patients with Anatomical Dual Mobility acetabular components were included. Markers were implanted in the liners using a drill guide. Static RSA recordings and patient reported outcome measures were obtained at post-op and 1-year follow-up. Dynamic RSA recordings were obtained at 1-year follow-up during a passive hip movement: abduction/external rotation, adduction/internal rotation (modified FABER-FADIR), to end-range and at 45° hip flexion. Liner- and neck movements were described as anteversion, inclination and rotation. Liner movement during modified FABER-FADIR was detected in 12 of 16 patients. Median (range) absolute liner movements were: anteversion 10° (5–20), inclination 6° (2–12), and rotation 11° (5–48) relative to the cup. Median absolute changes in the resulting liner/neck angle (small articulation) was 28° (12–46) and liner/cup angle (larger articulation) was 6° (4–21). Static RSA showed changes in median (range) liner anteversion from 7° (-12–23) postoperatively to 10° (-3–16) at 1-year follow-up and inclination from 42 (35–66) postoperatively to 59 (46–80) at 1-year follow-up. Liner/neck contact was associated with high initial liner anteversion (p=0.01). The polyethylene liner moves over time. One year after surgery the liner can move with or without liner/neck contact. The majority of movement is in the smaller articulation between head and liner.

Authors 5

1. Peter Bo Jørgensen

   Aarhus University Hospital

   Affiliation as printed

   AutoRSA Research Group, Orthopeadic Research Unit Aarhus University Hospital, Aarhus, Denmark

2. Bart L. Kaptein Aachen Biomechanics and Imaging Group Department of Orthopaedics, Leiden University Medical Center

   Leiden University Medical Center

   Affiliation as printed

   Biomechanics and Imaging Group, Department of Orthopaedics, Leiden University Medical Center, Leiden, Netherlands

3. Kjeld Søballé

   Aarhus University Hospital

   Affiliation as printed

   AutoRSA Research Group, Orthopeadic Research Unit Aarhus University Hospital, Aarhus, Denmark

   Department of Orthopaedic Surgery Aarhus University Hospital, Aarhus, Denmark

4. Stig Storgaard Jakobsen

   Aarhus University Hospital

   Affiliation as printed

   Department of Orthopaedic Surgery Aarhus University Hospital, Aarhus, Denmark

5. Maiken Stilling

   Aarhus University Hospital

   Affiliation as printed

   AutoRSA Research Group, Orthopeadic Research Unit Aarhus University Hospital, Aarhus, Denmark

   Department of Orthopaedic Surgery Aarhus University Hospital, Aarhus, Denmark