Total knee implant posterior stabilised by a third condyle: Designevolution and post-operative complications
Background: Despite excellent long-term outcomes, posterior stabilisation by a third condyle continuesto receive unwarranted criticism regarding patellar complications and instability.
Hypothesis: Complication rates with a tri-condylar posterior-stabilised implant are similar to those withother posterior-stabilised prostheses and have diminished over time due to improvements in prosthesisdesign.
Material and methods: Post-operative complications and revision rates were assessed retrospectively ina prospective cohort of 4189 consecutive patients who had primary total knee arthroplasty (TKA) usinga tri-condylar posterior-stabilised implant (Wright-Tornier) and were then followed-up for at least 24months. The analysis included 2844 knees. The prosthesis generations were HLS1®, n = 20; HLS2®, n = 220;HLS Evolution®, n = 636; HLS Noetos®, n = 1373; and HLS KneeTec®, n = 595. Complications were comparedacross generations by applying Fisher’s exact test, and survival was compared using the Kaplan-Meiermethod.
Results: At last follow-up, there had been 341 (12%) post-operative complications in 306 (10.8%) knees,including 168 (5.9%) related to the implant, 41 (1.4%) infections, and 132 (4.6%) secondary complicationsunrelated to the implant. Re-operation was required for 200 complications (7%), including 87 (3.1%) con-sisting in revision of the prosthesis. Implant-related complications were stiffness (n = 67, 2.4%), patellarfracture (n = 34, 1.2%), patellar clunk syndrome (n = 25, 0.9%), patellar loosening (n = 3, 0.1%), tibial/femoralloosening (n = 15, 0.5%), polyethylene wear (n = 3, 0.1%), and implant rupture (n = 1, 0.04%). Significantdifferences across generations were found for stiffness (P < 0.0001), patellar fracture (P = 0.03), clunk syn-drome (P = 0.03), and polyethylene wear (P = 0.004), whose frequencies declined from one generation tothe next. Overall 10-year survival was 92% with no significant difference across generations (P = 0.1).
Discussion: Outcomes of tri-condylar posterior-stabilised TKA are similar to those obtained using otherposterior-stabilised implants. Neither patellar complications nor instability are more common, andimprovements in implant design have contributed to correct early flaws.Level of evidence: IV, historical cohort, retrospective assessment of prospectively collected data.
© 2016 Elsevier Masson SAS. All rights reserved.
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