Mid to long-term outcomes of the primary constrained condylar knee arthroplasty

Abstract

BackgroundThe design of the constrained condylar knee (CCK) implant is meant to provide significantly more varus-valgus and anterior-posterior stability than a standard implant system. We hypothesized that while an increased constraint in design may lead to radiographic signs of loosening, the pain and functional outcome scores for patients with constrained implants remain acceptable at a mid to long term follow-up. Methods113 patients who underwent a primary TKA with a CCK implant by a single surgeon between the years 2008–2015 were contacted. 28 patients (30 knees) responded and returned for evaluation, which consisted of a Knee Society Score questionnaire and repeat radiographs. The average time to follow-up was 49.5 months. ResultsPain outcome scores (total of 30 knees) included, 19 excellent (63.3%), 7 good (23.3%) and 4 poor outcomes (13.3%). Function scores included 19 excellent (63.3%), 2 good (6.6%), 4 fair (13.3%), and 5 poor (16.7%) outcomes. There was a significant difference (p = 0.032) in pain scores between patients with no signs of radiographic lucency (mean pain score of 88.6) and patients with signs of implant loosening (mean pain score of 78.3). There was no significant difference in functional scores. ConclusionThe CCK implant is an acceptable option for a total knee arthroplasty which requires the extra stability not provided by a standard implant system. More studies with larger sample sizes, different populations and longer follow-up are needed to further evaluate outcomes in CCK implant recipients.