Traumatic Dislodgement of Tibial Polyethylene Insert after a High-Flex Posterior-Stabilized Total Knee Replacement

Abstract

Many pathologic entities can produce a painful total knee replacement (TKR) that may lead to potential prosthetic failure. Polyethylene insert dissociation from the tibial baseplate has been described most frequently after mobile-bearing and cruciate-retaining TKRs. However, only 3 tibial insert dislocations in primary fixed-bearing High-Flex posterior-stabilized TKRs have been reported. We present a new case of tibial insert dislocation in a High-Flex model that shares similarities and differences with the cases reported, facilitating the analysis of the potential causes, which still remain undefined.

Traumatic dissociation of the tibial insert with patellar tendon rupture after high-flex posterior-stabilized Genesis II total knee arthroplasty

“… 3 , 4 , 5 Such an event is very rarely seen with fixed bearing high flex posterior stabilized TKA and there are only four cases reported till now. 6 , 7 , 8 , 9 All the cases used Genesis II (Smith & Nephew, Memphis, Tennessee, USA), similar to our case.…”

“…They have also stated that repeated micro motion leads to progressive wear of the thin posterior dovetails resulting into subsequent dissociation. Astoul Bonorino et al 9 reported a case of traumatic dislodgement of the insert at 32 weeks after TKA. They have associated failure of the posterior locking mechanism to be the reason for dissociation.…”

“…We have reported a late presentation similar to Lee et al 8 which is in contrast to other studies presenting within two years of TKA. 6 , 7 , 9 All the studies have reported damage to the posterior lips (medial and/or lateral) of the non-articulating surface of the polyethylene insert and anterior dislocation. These findings suggest damage of the thin posterior dovetails of the insert along with the failure of posterior locking mechanism leading to dissociation.…”

“…Astoul Bonorino et al 9 established three potential risk factors for liner dissociation which includes: error in surgical technique, prosthesis design, and patient-related factors. Various factors like flexion-extension gap balancing, ligamentous instability and inadequate capture of the insert on the base plate locking mechanism might play a role.…”

“… 3 , 4 , 5 Till date dissociation of the polyethylene insert after high-flex posterior stabilized (PS) Genesis II TKA (Smith & Nephew, Memphis, Tennessee, USA) has been described in four reports. 6 , 7 , 8 , 9 Causes of dissociation described in these reports are thought to be due to trauma or failure of the locking mechanism.…”