Case Report: Failure of Rotating-hinge Total Knee Prosthesis by Disengagement of the Hinge-post Extension

Abstract

Background Although modern-generation rotating-hinge knee implants have been modified to mitigate earlier complications related to aseptic loosening with these devices in revision TKAs, there are few, if any, reports of failure related to the hinge mechanism in these prostheses. Case Description We present a case of disengagement of the hinge-post extension in a contemporary rotating-hinge knee prosthesis originally implanted during revision surgery for instability and extensor mechanism insufficiency. We hypothesize the screw home kinematics of the knee resulted in a counterclockwise torque, contributing to the hinge post locking screw disengagement in this case. Literature Review Although some authors have reported complications and failures related to aseptic loosening with rotating-hinge knee prostheses, there have been no reports regarding complications related to the hinge mechanism, which simultaneously links and permits rotation between the femoral and tibial components. Clinical Relevance Arthroplasty surgeons who use rotating-hinge knee prostheses need to be aware of this potential mode of failure. Design modifications, including more secure locking mechanisms and side-specific implants, may avoid this complication.

Recurring intraprosthetic dislocation of rotating-hinge total knee prosthesis. Effect of implant design on intrinsic stability

“…The outcomes in terms of implant stability are generally very good [5,9]. However, these implants have limitations that cannot be ignored, as evidenced by the case reported here and other published case reports [3,[11][12][13][14].…”

“…Unscrewing of the hinge post-extension and its disengagement from the tibial baseplate have previously been reported [12]. The kinematics of a knee after arthroplasty are similar to the one of a healthy knee [15].…”

“…It is hypothesized that repeated flexion -extension cycles increases the risk of separation in right knees and reduces this risk in left knees. In fact, the case reported here and 5 of the 6 similar published cases involve the right knee [12,14]. This risk could be reduced by developing side-specific implants, or adding a lock nut or reverse threads in implants destined for the right knee.…”

“…But this procedure is not without complications and failures [3,10]. Among these complications, ones related to the hinge itself are rare and have been described only in clinical case reports [11][12][13]. Analyzing these particular complications can help us understand limitations in the implant's design and can provide avenues to preventing these complications.…”

Posterior Dislocation of the Hinge-Post Extension in a Rotating Hinge Total Knee Prosthesis

“…Recently, Chuang and colleagues reported failure of a rotating hinge megaprosthesis due to breakage of the tibial polyethylene stopper [14]. Despite these reports of hinge failure, only 2 reports of atraumatic disengagement of the rotating hinge stem have been described in the literature [10, 11]. Here, we report a case of atraumatic disengagement of the rotating stem due to opening of the flexion gap, leading to subsequent posterior dislocation of the hinge and anterior knee dislocation in a patient with a history of multiple total knee arthroplasty revisions.…”