B Marion1, D Huten2, P Boyer1, C Jeanrot1, P Massin3. 1. Service de chirurgie orthopédique, hôpital Bichat-Claude-Bernard, 46, rue Henri-Huchard, 75877 Paris cedex 18, France; EA REMES, université Paris-Diderot, Sorbonne Paris Cité, 75010 Paris, France. 2. Service de chirurgie orthopédique, CHU de Rennes, 16, boulevard Bulgarie, BP 90347, 35203 Rennes cedex 2, France. 3. Service de chirurgie orthopédique, hôpital Bichat-Claude-Bernard, 46, rue Henri-Huchard, 75877 Paris cedex 18, France; EA REMES, université Paris-Diderot, Sorbonne Paris Cité, 75010 Paris, France. Electronic address: philippe.massin@bch.aphp.fr.
Abstract
BACKGROUND: Highly congruent total knee prostheses were introduced in the 1990s in the hope of decreasing polyethylene wear, thereby minimising loosening and particle-induced peri-prosthetic osteolysis. Despite promising long-term outcomes, substantial rates of aseptic loosening were reported with conventional gamma-irradiated polyethylene inserts, suggesting that highly reticulated polyethylene should be used instead. We assessed medium-term outcomes of the Wallaby I® total knee prosthesis with a deep-dished tibial insert made of conventional gamma-irradiated polyethylene. HYPOTHESIS: We hypothesised that the deep-dished Wallaby I® prosthesis was associated with similar or lower rates of aseptic loosening and peri-prosthetic osteolysis compared to posterior-stabilised prostheses. MATERIALS AND METHODS: At our institution, 121 consecutive patients underwent total knee arthroplasty (TKA) with a deep-dished cemented prosthesis (Wallaby I®, Sulzer/Centerpulse, Zürich, Switzerland) between 2001 and 2005. Among them, 89 had complete follow-up data over a 4-year period and a mean follow-up of 96 months. We retrospectively analysed the clinical and radiographic IKS scores in these 89 patients. RESULTS: Osteolysis with aseptic loosening required revision TKA of 10 knees after a mean follow-up of 81 months. Mean 9-year prosthesis survival was 88±17%. Four inserts exhibited evidence of delamination. A fracture of the postero-medial aspect of the tibial baseplate beneath a zone of insert wear was found in 1 knee and gross mobility of the insert on the baseplate in 6 knees. The other 79 patients had good clinical and radiographic outcomes with a mean range of active knee flexion of 108±15°. DISCUSSION: The medium-term outcomes in our study were inferior to those reported with posterior-stabilised tibial components. Sporadic variations in polyethylene quality may explain the cases of osteolysis (shelf oxidation). In addition, the increased shear stresses related to the deep-dish design may increase backside wear, thereby compromising insert fixation to the baseplate. We believe the Wallaby I® prosthesis should no longer be used, and we recommend computed tomography follow-up of patients harbouring this prosthesis. LEVEL OF EVIDENCE: Level IV (retrospective study).
BACKGROUND: Highly congruent total knee prostheses were introduced in the 1990s in the hope of decreasing polyethylene wear, thereby minimising loosening and particle-induced peri-prosthetic osteolysis. Despite promising long-term outcomes, substantial rates of aseptic loosening were reported with conventional gamma-irradiated polyethylene inserts, suggesting that highly reticulated polyethylene should be used instead. We assessed medium-term outcomes of the Wallaby I® total knee prosthesis with a deep-dished tibial insert made of conventional gamma-irradiated polyethylene. HYPOTHESIS: We hypothesised that the deep-dished Wallaby I® prosthesis was associated with similar or lower rates of aseptic loosening and peri-prosthetic osteolysis compared to posterior-stabilised prostheses. MATERIALS AND METHODS: At our institution, 121 consecutive patients underwent total knee arthroplasty (TKA) with a deep-dished cemented prosthesis (Wallaby I®, Sulzer/Centerpulse, Zürich, Switzerland) between 2001 and 2005. Among them, 89 had complete follow-up data over a 4-year period and a mean follow-up of 96 months. We retrospectively analysed the clinical and radiographic IKS scores in these 89 patients. RESULTS:Osteolysis with aseptic loosening required revision TKA of 10 knees after a mean follow-up of 81 months. Mean 9-year prosthesis survival was 88±17%. Four inserts exhibited evidence of delamination. A fracture of the postero-medial aspect of the tibial baseplate beneath a zone of insert wear was found in 1 knee and gross mobility of the insert on the baseplate in 6 knees. The other 79 patients had good clinical and radiographic outcomes with a mean range of active knee flexion of 108±15°. DISCUSSION: The medium-term outcomes in our study were inferior to those reported with posterior-stabilised tibial components. Sporadic variations in polyethylene quality may explain the cases of osteolysis (shelf oxidation). In addition, the increased shear stresses related to the deep-dish design may increase backside wear, thereby compromising insert fixation to the baseplate. We believe the Wallaby I® prosthesis should no longer be used, and we recommend computed tomography follow-up of patients harbouring this prosthesis. LEVEL OF EVIDENCE: Level IV (retrospective study).