Comparisons of Prosthesis Fitness, Early Recovery Patterns, Functional Outcomes and Patient Satisfaction Between E.Motion-Pro, a New Mobile Bearing System and Genesis II, an Established Successful System

Total knee arthroplasty (TKA) is a satisfactory treatment option for patients with advanced knee diseases that are intractable with other modalities in terms of pain relief, functional restoration, and deformity correction. Unfortunately, however, many patients have to go through a recovery period of several months during which they experience considerable pain and suffer from incompletely restored functions. In recent years, to improve the quality of life during early recovery period after TKA, great efforts have been made in multiple areas including the use of minimally invasive surgical technique, improved pain management protocols, and postoperative rehabilitation protocols. Nonetheless, this almost inevitable presence of painful and disabling recovery period is a major concern to patients scheduled for or considering TKA as a treatment option. Furthermore, this issue can become a more serious obstacle to very elderly patients who have to balance the benefits of remaining years with improved functions from replaced knees and the burden of recovery duration after TKA.

In theory, the use of a better fitting prosthesis with sound kinematic performance can shorten the duration of recovery period and improve the quality of life by reducing pain and facilitating functional recovery. Better fitting prostheses allegedly less involve prosthesis overhang at femoral condylar level, which can cause impingement symptoms and at anterior flange area, which can cause patellofemoral symptoms. Prosthesis providing better kinematic performance such as natural motion and joint stability throughout motion arc can reduce pain and discomfort in early recovery period and shorten the duration of recovery period.

Recently, E.Motion-PS-Pro (B.Braun-Aesculap, Tuttlingen, Germany), a new mobile bearing knee system with a unique ball and socket post-cam mechanism was developed. This new prosthesis was designed to achieve better prosthesis fitting, to minimize bone loss from box preparations for post-cam mechanism, to improve joint stability throughout motion arc, particularly in high flexion, and to reduce the risk for wear and fracture at the post by increasing contact area. If the intended design rationales work out well, this prosthesis shall reduce soft tissue impingement and provide better kinematic performances, which reduces pain and facilitates functional restoration.

Therefore, the current investigators aim to determine (1) whether the use of E.Motion-PS-Pro improves prosthesis fitness for the femur and tibia in terms of under- or over-hang incidence compared to an established successful prosthesis, Genesis II (Smith & Nephew, Memphis, U.S.A.), (2) whether patients with this new prosthesis experience less pain and faster wound healing in early recovery phase, (3) whether patients with E.Motion-Pro reach functional plateaus faster than patients with Genesis II and the functional plateaus of patients with E.Motion-Pro are higher than those of patients with Genesis II. The investigators hypothesize that (1) E.Motion-Pro reduces the incidence of prosthesis under- or over-hang, (2) patients with E.Motion-Pro experience less pain and faster wound healing in early recovery phase, and (3) patients with E.Motion-Pro reach functional plateau faster and the functional outcomes at 1 year are better in patients with E.Motion-Pro than those with Genesis II.