Causes of failure of the Kinemax Plus total knee replacement in the first five years.

In order to investigate whether any single batch of polyethylene inserts was responsible for premature failure of total knee replacements (TKR), we performed a retrospective database review of 1133 consecutive primary Kinemax Plus TKR performed by 2 surgical teams between January 1992 and January 2001 at our institution. Cases re-operated in any way within 5 years of the index arthroplasty were identified, case notes studied and radiographs reviewed. The causes contributing to the premature failure of the implants were identified where possible and the polyethylene lot numbers were recorded. Nineteen cases were known to have been revised, 7 cases for deep infection of the prosthesis and 12 for aseptic failure. In 10 cases, an identifiable technical error had contributed to the early failure of the implant. In 4 of these cases, there was inadequate tissue balancing in patients with a significant pre-operative valgus deformity. In 2 cases, the tibial base plate was inserted in a varus mal-alignment. There was one extended tibial component, one internally rotated femoral component, one oversized femoral component and one femoral component with inadequate fixation. Two further cases failed aseptically, one with a fracture of the medial tibial plateau and one idiopathic. The lot numbers of the polyethylene inserts were all different. This study confirms that the premature failure rate of the Kinemax Plus TKR is low. Although a "bad batch" of polyethylene has been suggested as a cause for early failure in TKR, in this series, surgical error was the predominant cause.