title: Medium-term osteolysis with the Wallaby I® deep-dished total knee prosthesis.
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.
  
  
  OBJECTIVE
  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.
  
  
  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°.
  
  
  CONCLUSIONS
  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.
  
  
  METHODS
  Level IV (retrospective study).
authors.affiliation: 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.
authors.forename: B
authors.initials: B
authors.lastname: Marion
authors.affiliation: Service de chirurgie orthopédique, CHU de Rennes, 16, boulevard Bulgarie, BP 90347, 35203 Rennes cedex 2, France.
authors.forename: D
authors.initials: D
authors.lastname: Huten
authors.affiliation: 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.
authors.forename: P
authors.initials: P
authors.lastname: Boyer
authors.affiliation: 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.
authors.forename: C
authors.initials: C
authors.lastname: Jeanrot
authors.affiliation: 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.
authors.forename: P
authors.initials: P
authors.lastname: Massin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000295:instrumentation; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D010014:Osteolysis / Q000209:etiology; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D012189:Retrospective Studies
keywords: Deep-dished total knee arthroplasty; Loosening; Particle-induced osteolysis; Revision total knee arthroplasty