Five cases of tibial post fracture in posterior stabilized total knee arthroplasty using Prolong highly cross-linked...

Fracture of a polyethylene tibial post after a posterior stabilized total knee arthroplasty (PS-TKA) is an uncommon but severe complication. We report five cases of non-traumatic fracture of a tibial polyethylene post that occurred with Prolong highly cross-linked polyethylene with the NexGen LPS-Flex total knee prosthesis.

A Joint Reconstruction database for a high volume arthroplasty unit was used to identify all cases of revision of Prolong polyethylene used in PS-TKA. Five cases were identified as being revised because of a broken tibial post.

All five cases presented with a combination of sudden and increasing pain, instability and giving way, in previously well-functioning TKAs. There was no history of trauma or precipitating incident. Mean time from primary TKA to presentation and diagnosis of post fracture was 67.7 months (range 24-108). All five cases were successfully treated by revision, in the form of a liner exchange to a standard ultra-high molecular weight polyethylene (UHMWPE) bearing of the same thickness. The five cases occurred from a consecutive series of 955 total PS-TKAs with Prolong. This gives a conservative estimate of the frequency of this complication of 0.52%. This would give a risk of a tibial post fracture in approximately one in every 200 TKAs with this specific implant and bearing combination.

To our knowledge, this is the first report of a non-traumatic fracture to the tibial post with this bearing type. We would advocate against the routine use of Prolong highly crosslinked polyethylene in PS-TKA.