No Long-term Difference Between Fixed and Mobile Medial Unicompartmental Arthroplasty

Abstract

Background Early studies in the literature reported relatively high early minor reintervention rate for the mobilebearing unilateral knee arthroplasty (UKA) compared with short-and midterm survivorship after fixed-or mobilebearing UKA. However, whether the long-term function and survivorship are similar is unclear. Questions/purposes We therefore asked whether (1) mobile-or fixed-bearing UKAs have comparable function (as measured by the Knee Society scores); (2) mobile-and fixed-bearing UKA have comparable Knee Society radiographic scores; and (3) the long-term survivorship is comparable. Methods We retrospectively reviewed 75 patients (79 knees) with a fixed-bearing UKA and 72 patients (77 knees) with a mobile-bearing UKA operated on between 1989 and 1992. Mean age of the patients was 63 years; gender and body mass index (26 kg/m 2 ) were comparable in the two groups. We obtained Knee Society function and radiographic scores and determined survival. The minimum followup was 15 years (mean, 17.2 ± 4.8 years; range, 15-21.2 years).

Survivorship and clinical outcome of the minimally invasive Uniglide medial fixed bearing, all-polyethylene tibia, unicompartmental knee arthroplasty at a mean follow-up of 7.3years

“…However bearing dislocation may occur in 1-5.3% of medial UKAs [12,13] and has been identified as the fourth most frequent mode of failure for mobile-bearing implants [14]. Fixed bearing designs have been shown in several studies to have equivalent clinical and radiographic outcomes compared to mobile-bearing implant designs at mid and long term follow up [15]. A fixed bearing eliminates the risk of bearing dislocation, however some studies have shown higher revision rates for all-polyethylene tibial components compared to those that utilize metal-backed implants [16][17][18].…”

Effect of Polyethylene Crosslinking and Bearing Design on Wear of Unicompartmental Arthroplasty

“…However, survivorship after unicompartmental arthroplasty is often lower than that after TKA [6,7]. Loosening, lysis, and wear and polyethylene damage continue to be important factors affecting outcomes and have been implicated in up to 22% to 45% of revision surgeries after UKA [8,9].…”

Unicompartmental knee arthroplasty: state of the art

“…Survival rates of lateral UKA increased up to 92% at a mean follow-up of 4 years and good functional outcomes were reported by Weston-Simons et al 65. Comparative studies on medial UKAs were performed by Parratte et al 66 and Whittaker et al ;67 they found equivalent mid-term and long-term functional outcomes and survivorship rates of mobile-bearing versus fixed-bearing implants. The predominant reasons for revision were progression of OA and aseptic loosening in both fixed-bearing and mobile-bearing UKA.…”

“…A joint space height difference <2 mm was significantly associated with shorter medial UKA survival 29. Failures related to a lower position of the prosthetic joint line were due to loosening, whereas failures related to a higher position of the prosthetic joint space were due to early polyethylene wear and progression of OA in the contralateral compartment 29 40 47 66. As Chatellard et al 29 stated, UKA acts as a wedge that compensates for the joint damage, which restores normal kinematics and blocks the vicious circle of medial femorotibial OA 74…”

“…As previously mentioned, wear is another mode of failure which is mostly seen in fixed-bearing designs of UKA 43 66. Higher stresses are generated in these types of designs, often in combination with a metal-backed tibial tray, which allows only a certain polyethylene thickness.…”