51

• Early migration in unicompartmental knee arthroplasty with the Persona^® Partial Knee: a radiostereometric study with 2 years of follow-up

Jantsje Pasma¹, Brechtje Hesseling¹, Ian Blom^1,2, Dieu Donné Niesten¹, Hennie Verburg¹, Nina Mathijssen¹

¹Reinier Haga Orthopedisch Centrum, Zoetermeer, the Netherlands. ²Department of Radiology, Reinier de Graaf Gasthuis, Delft, the Netherlands

Introduction: Unicompartmental knee arthroplasty (UKA) is used to treat patients with arthritis limited to one compartment of the knee. Aseptic loosening is a common problem in UKA and one of the most common indications for revision arthroplasty. To show early satisfactory implant stability of the Persona^® Partial Knee (PPK, Zimmer Biomet, Warsaw, IN), a cemented medial fixed-bearing unicompartmental knee, we investigated the early migration using model-based radiostereophotogrammetric analysis (mRSA) and evaluated the clinical results.

Material and Method: In this prospective cohort study, 27 primary PPKs were implanted. Radiographs were obtained direct postoperatively, at 6 weeks, 6 months, 1 year and 2 years postoperatively. Migration of the tibia and femur component was calculated using mRSA in terms of translations and rotations. To obtain precision, double examination was performed 1 year postoperatively. To evaluate the clinical results, PROMs (NRS pain, KOOS-PS, OKS, EQ-5D) were registered.

Results: At 2 years postoperatively, the mean (SD) translation of the femur component was 0.14 (0.34), 0.06 (0.18) and 0.06 (0.29) mm along the x-, y- and z-axis respectively. The mean (SD) rotation of the femur component was 0.16 (0.33), -0.05 (0.35) and 0.17 (0.55) degrees around these axes. The mean (SD) translation of the tibia component was 0.08 (0.20), -0.18 (0.34) and 0.001 (0.206) mm along these axes. The mean (SD) rotation of the tibia component was 0.45 (1.13), 0.10 (0.63), -0.57 (1.21) degrees around these axes. Precision intervals for both translation and rotation varied from 0.07 to 0.43 mm and from 0.19 to 0.79 degrees, respectively. All PROMs improved after 2 years compared to preoperative PROMs.

Interpretation and conclusion: The Persona^® Partial Knee shows low migration of both the femur and tibia component and good clinical results at 2 years follow-up. Long-term follow-up is needed to investigate the relation between early migration and long-term results.

Keywords: Unicompartmental knee arthroplasty, model-based radiostereophotogrammetric analysis, early migration

52

• Comparison of cementless double-peg, cemented single-peg and cemented double-peg femoral component migration after medial Oxford unicompartmental knee replacement – A 5-year randomized RSA study.

S. B. Mosegaard¹, F. Madsen¹, A. Odgaard³, P.W. Kristensen⁴, K. Søballe^1,2, M. Stilling^1,2

¹Department of Orthopaedic Surgery, Aarhus University Hospital, 8200 Aarhus N, Denmark. ²Department of Clinical Medicine, Aarhus University, 8200 Aarhus N, Denmark. ³Department of Orthopaedic Surgery, Rigshospitalet, Copenhagen University Hospital, 2100 Copenhagen, Denmark. ⁴Department of Orthopaedic Surgery, Vejle Hospital, 7100 Vejle, Denmark.

Introduction: Many studies have investigated the tibial component migration but the knowledge on femoral component migration is limited. This study aimed to examine the potential fixation difference between cemented single-peg (CS), cemented double-peg (CD) and cementless double-peg (CLD) femoral components of medial unicompartmental knee arthroplasty (UKA).

Material and methods: 80 patients (mean age = 63 years, 48 males) with medial knee osteoarthritis were randomized 3-ways to cemented single-peg UKR (n=29), cemented double-peg UKR (n=26) or cementless double-peg femoral UKR components (n=25). Patients were followed 5 years postoperatively with RSA and bone mineral density (BMD).

Results: At 5-years follow-up, femoral component total translation was comparable between the CS, CD and CLD group (p=0.60). The femoral internal/external rotation was 0.21 degrees (95% CI: 0.01 – 0.41) for the CS group, 0.60 degrees (95% CI: 0.39 – 0.82) for the CD group, and 0.45 degrees (95% CI: 0.24 – 0.67) for the CLD group (p=0.38), with higher rotation in the CD group than the CS group (p=0.01). There was no correlation between periprosthetic BMD and component migration.

Interpretation and conclusion: Considering cemented single-peg femoral components as reference, cemented double-peg components showed slightly higher internal/external rotation at 5-years follow-up, which although statistically significant might not be clinically relevant. There was no dependency on periprosthetic bone mineral density. 

Keywords: RSA, femoral component migration, cementless, cemented, unicompartmental knee replacement, bone mineral density.

53

• Mid-term tibial component fixation of a fixed-bearing and a mobile-bearing cemented unicompartmental knee replacement. A randomized controlled RSA study with 5-year follow-up.

Daan Koppens^1,3, Søren Rytter³, Torben Bæk Hansen¹, Maiken Stilling^2,3

¹ University Clinic for Hand, Hip and Knee Surgery, Holstebro Central Hospital, Denmark.

² Department of Clinical Medicine, Aarhus University, Aarhus N, Denmark. ³ Department of Orthopedic Surgery, Aarhus University Hospital, Aarhus N, Denmark.

Introduction: Tibial components of a mobile-bearing (MB) and fixed-bearing (FB) unicompartmental knee replacement (UKR) distribute stress differently at the implant/bone interface, which may lead to a difference in fixation of the tibial component. Yet, early tibial component migration (2 years) of the MB and FB UKR was found to be equal.  The aim of this study was to evaluate mid-term tibial component migration of the MB and FB UKR.

Material and Method: A patient-blinded, randomized controlled RSA study with 60 months follow-up was performed. 65 patients were randomized to a MB UKR (N = 33) or a FB UKR (N = 32). Stereoradiographs were obtained postoperatively, at 4, 12, 24, and 60 months. Model-based RSA software was used to measure tibial component migration. Mixed model analysis was used for statistical evaluation.

Results: Tibial component migration (translations, rotations, and MTPM) was similar between UKRs, but with a pattern of some migration throughout follow-up. Between 24 and 60 months, MB UKR migrated (MTPM) 0.01 mm (95% CI -0.05 – 0.07) and the FB UKR migrated 0.10 mm (95% CI 0.04 – 0.17).MTPM at 60 months for the MB UKR was 0.43 mm (95% CI 0.33 – 0.53) and for the FB UKA 0.40 mm (95% CI 0.31 – 0.48). Continuous migration was found for 1 MB UKR (N = 28) and 3 FB UKRs (N = 28) in phase 2 (12-24 months), and for 2 MB UKRs (N = 25) and 5 FB UKRs (N = 24) in phase 3 (24-60 months).

Interpretation and Conclusion: Tibial components of the MB and FB UKR showed equal and low mid-term migration. No clinically significant migration was seen at 5 years and thus low long-term revision rates can be expected for both implants.

Keywords

Randomized controlled trial, knee, fixed-bearing, mobile-bearing, unicompartmental knee arthroplasty, radiostereometric analysis.