Congruent rotating tibial plateaus are designed to minimise wear after total knee arthroplasty (TKA). The Score™ prosthesis has a congruent rotating tibial plateau, a deep trochlear groove, and uses a computer-assisted navigation system for ligament balancing. Although this prosthesis is widely utilized, no accurate data on outcomes are available.
The innovative features of the Score™ prosthesis, most notably patellar replacement with a highly constrained femoral component, do not jeopardize implant survival.
Patients and methods
In a pilot study, we retrospectively evaluated outcomes of 19 patients treated with Score™ knee replacement between February and October 2006 (mean age, 66.8years; range, 58–82years). The evaluation criteria were the International Knee Society (IKS) scores and prosthesis survival rate estimated using Kaplan-Meier plots with failure defined as revision need to change the prosthesis.
Mean follow-up was 35.3months. The IKS knee score increased from 27.4 (5–60) preoperatively to 81.4 (45–99) at last follow-up (P<0.0001). Mean mechanical axis was 181.2° (180–186°), with 16 between 180° and 183°. Revision surgery was required in five cases (for patellar complications with combined motion-range limitation in flexion (<90°) and extension (5–20°) in three cases, isolated motion-range limitation in one case, and recurvatum deformity with instability in one case). Prosthesis survival was 82% (73–91%) after 24months and 65% (51–78%) after 44months.
The deep trochlear groove femoral component resulted in patellar complications, which were the most common reasons for revision surgery, together with motion-range limitation and instability possibly related to improper use of the navigation system. This small retrospective case-series study showed an unusually low prosthesis survival rate probably related to the implant design. We no longer use the Score™ prosthesis, despite the availability of a dedicated navigation system, and we recommend careful monitoring of patients who have this prosthesis.
Level of evidence
Level IV, retrospective study.Le texte complet de cet article est disponible en PDF.
Keywords : Knee prosthesis, Rotating platform, Computer-assisted implant surgery, Patello-femoral, Instability