Constraint choice in revision knee arthroplasty: study protocol of a randomised controlled trial assessing the effect of level of constraint on postoperative outcome

Abstract

IntroductionThe proper management of total knee arthroplasty (TKA) in patients with severe deformities regarding the preferable prosthetic design and the required amount of constraint is a controversial subject. In the absence of any high-level clinical evidence, we designed a randomised clinical trial to investigate if rotating hinged (RTH) and constrained condylar knee (CCK) designs yield similar outcomes.Methods and analysisThis study is a multicentre, randomised clinical trial including two groups of 85 patients. Patients will be randomised to a CCK knee design group or an RTH knee design group. Patients will be followed for 2 years. The study will be designed as an equivalence trial. The primary study outcome will be the postoperative functional outcome as measured by the self-administered Knee Injury and Osteoarthritis Outcome Score. Secondary outcomes will be postoperative joint awareness during various activities of daily living as measured by the Forgotten Joint Score-12, the Knee Society Score, along with the incidence and location of radiolucent lines using the Knee Society TKA radiographic evaluation system.Ethics and disseminationThis study is approved by the ethics committee of the Landesärztekammer Brandenburg ((S 10(a)/2013) from 27.08.2013, amended on 25.04.2016) and will be conducted according to the principles of the World Medical Association Declaration of Helsinki and the ISO14155:2011.Trial registration numberDRKS00010539.

Hot spots and trends in knee revision research since the 21st century: a bibliometric analysis

“…As for constraint, rotating hinge prosthesis and constrained condylar prosthesis are two research points (28)(29)(30)(31). The comparison between the outcomes of the two has never stopped and the controversy still exists (32,33).…”

The knee prosthesis constraint dilemma: Biomechanical comparison between varus‐valgus constrained implants and rotating hinge prosthesis. A cadaver study

“…This success rate has led to technological improvements in prostheses implanted during revision surgery. Prostheses with a higher level of constraint are needed in patients with greater ligament instability or bone stock loss 6–8 …”

“…Early hinged models, due to their rigidity, obtained poor 5‐year survival rates close to 75% 17 . However, the latest RHK models have achieved survival rates beyond 80% 10‐year survival, depending on the series consulted 6,18,19 . These results have led to the expansion of the classic indications for RHKs to the extent that they now share indications with CCK 18–20 .…”

Analysis of Biomechanical Differences Between Condylar Constrained Knee and Rotating Hinged Implants: A Numerical Study

“…Clinical studies have shown that when implant selection is guided by inherent stability of the knee, CCK and RTH knee designs have similar outcomes [6]; Fuchs et al [33] found no significant differences in terms of Hospital for Special Surgery Score, Knee Society Score, Pain and Tegner score in their retrospective cohort study, while standard condylar revision implants yielded better postoperative mobility but had a lower Short Form 36 Mental Component Score: this latter finding may then imply that patients tolerate the RTH design better than the standard condylar revision implant [7]. Walker et al [34] also compared the RTH design with standard condylar revision in a cohort study, finding a high correlation in performance between the operated and nonoperated side in the RTH group, thus indicating the hinges as capable of matching the nonoperated knee performance.…”

“…Indeed, different levels of constraint for TKA can be considered for revision surgeries because both semiconstrained and hinged implants guarantee more stability than primary TKA implants. The selection of the correct constraint level is therefore of paramount importance in this context [7,8].…”