Background: Radiostereometric analysis (RSA) is an established high precision tool enabling us to detect early implant migration in total hip arthroplasty. The aim of this study is to present the RSA and clinical results of a new cementless hip stem and to compare those with established benchmarks.
Methods: A total of 45 patients (46 hips) undergoing total hip arthroplasty were available for full radiographic and clinical assessment at 2 years post-operatively. Mean patient age was 69 (range 43-85) years and mean body mass index was 29 (range 21-38) kg/m2 . RSA was undertaken at day 1, 6 weeks, 6 months and 1 and 2 years post-operatively. Oxford hip score and EQ-5D-5L scores were recorded preoperatively and at the same other time points. Results were compared to published data of established implants.
Results: At 2 years, mean subsidence and retroversion were 0.61 mm (standard deviation 0.7 mm, range -0.19 to 3.06 mm) and 0.44° (standard deviation 0.81°, range 0.98 to 3.29°), respectively. Stem migration occurred primarily in the first 6 weeks with no detectable subsidence or rotation at 6 months or 2 years. Mean Oxford hip score and EQ-5D-5L improved from 18.6 to 44.7, and 69 to 86, respectively. There was one cup-only revision and no revisions for stem loosening.
Conclusion: RSA serves as an accurate measure of femoral stem stability early in the post-operative period. Our data confirm that stability occurs as early as 6 weeks and is sustained at 2 years. The Paragon stem demonstrates stability parameters at 2 years that exceed other established benchmark implants.
Keywords: orthopaedic surgery; radiostereometric analysis clinical outcome; radiostereometric analysis total hip arthroplasty; uncemented hip stem migration.
© 2021 Royal Australasian College of Surgeons.