Can accuracy of component alignment be improved with Oxford UKA Microplasty® instrumentation?

Abstract

Background One factor in the long-term survivorship of unicompartmental knee arthroplasty is the accuracy of implantation. In addition to implant designs, the instrumentation has also evolved in the last three decades to improve the reproducibility of implant placement. There have been limited studies comparing mobile bearing unicompartmental knee arthroplasty with contemporary instrumentation and fixed bearing unicompartmental knee arthroplasty with conventional instrumentation. This study aims to determine whether the Microplasty instrumentation in Oxford unicompartmental knee arthroplasty allows the surgeon to implant the components more precisely and accurately. Methods A total of 150 patients (194 knees) were included between April 2013 and June 2019. Coronal and sagittal alignment of the tibial and femoral components was measured on postoperative radiographs. Component axial rotational alignment was measured on postoperative computer tomography. The knee rotation angle was the difference between the femoral and tibial axial rotation. A rotational mismatch was defined as a knee rotation angle of > 10°. Statistical analysis was performed using Student t test and Mann-Whitney nonparametric test. A p value < 0.05 was considered statistically significant in each analysis. Results Between April 2013 to June 2019, 112 patients (150 knees) received Oxford unicompartmental knee arthroplasty, one patient (2 knees) had Journey unicompartmental knee arthroplasty, and 37 patients (42 knees) received Zimmer unicompartmental knee arthroplasty. All femoral components in the Oxford group were implanted within the reference range, compared with 36.6% in the fixed bearing group ( p < 0.001). 88.3% of Oxford knees had tibial component falling within the reference range, whereas 56.1% of knees in the fixed bearing group fell within the reference range ( p < 0.001). 97.5% of Oxford knees had tibial slope that fell within reference range, whereas 53.7% fell within range for fixed bearing group ( p < 0.001). Femorotibial rotational mismatch of more than 10° was noted in 13.8% in Oxford group and 20.5% in fixed bearing group ( p = 0.04). Conclusion In conclusion, Microplasty instrumentation for Oxford mobile bearing unicompartmental knee arthroplasty is more accurate and precise compared to conventional fixed bearing unicompartmental knee arthroplasty in sagittal, coronal, and axial alignment. Prospective studies with long-term follow-up are warranted to investigate the clinical implications.

Reduced 5-Year Risk for Revision of the Oxford UKA Using New Instrumentation versus Conventional Instrumentation: A Registry Study of 12,867 UKAs

“…In addition to their findings, we found no difference in risk for revision for UKAs using the new instrumentation compared to conventional instrumentation in the first year after the UKA. Previous studies have proven a more accurate component alignment in UKAs using the new instrumentation compared to conventional instrumentation [15][16][17][18]. Component malalignment can induce failure mechanism such as increased…”

“…implantation through an intramedullary linked femoral drilling guide, a spoon-stylus system, and sizing spoon [12]. Recent results demonstrate improved and reproducible component positioning and alignment in UKAs using the new instrumentation compared to its predecessor, conventional instrumentation (Phase 3) [13][14][15][16][17][18][19].…”

Tibial cutting guide (resector) holding pins position and subsequent risks of periprosthetic fracture in unicompartmental knee arthroplasty: a finite element analysis study

“…The goal of UKA is to relieve pain and restore knee function by replacing the diseased compartment of the knee joint with an artificial implant, and the most common type is medial UKA due to high prevalence of medial osteoarthritis [ 21 , 22 ]. Following UKA, immediate weight bearing walking is allowed to facilitate early rehabilitation.…”

The medial condylar wall is a reliable landmark to kinematically align the femoral component in medial UKA: an in-silico study

“…It is likely that a large mismatch between the frontal orientation of the femoral and tibial implants could lead to poor implant interaction in the knee extension position, with risk of mobile liner dislocation [ 13 ]. However, this risk would probably be low, because the mobile-bearing and single radius design of the Oxford™ UKA makes it a forgiving implant regarding the risk of poor implants’ interaction (or interplay) [ 8 ]. To lower this risk, the MWMC could be used in conjunction with other methods to help improve the reliability of frontal KA positioning of the femoral UKA implant, mainly in situations where the surgeon has difficulty in assessing the native frontal orientation of the MWMC (e.g., improper cleaning of condylar osteophytes).…”