028. Does a long stem improve long term survivorship in cementless total knee arthroplasty? A matched cohort series of 98 standard stems versus 98 long stems at more than 10 years follow-up

J-L Prudhon, R Verdier, J Caton (Lyon, Grenoble)

Background : Even though cementing is the most common way to secure implants during primary total knee arthroplasty (TKA), since 1996, we have routinely been using cementless hydroxyapatite-coated TKA implants in order to preserve bone stock. Cementless monoblock long stems (MLS) were introduced in 2004 to improve alignment and tibial fixation when bone conditions are considered as poor or critical for standard stem (SS) cementless fixation. The purpose of this study was to compare the survivorship of cementless SS versus cementless MLS in critical bone conditions.

Material Methods : Among 635 cementless TKA procedures (posterior-stabilised mobile bearing) performed between 2002 and 2014, we selected and matched (1:1) two cohorts of TKAs – 98 cementless SS and 98 cementless MLS implanted in patients identified as having critical bone conditions: TKA after high tibial osteotomy, revision of unicompartmental knee arthroplasty, anterior tibial tuberosity transfer, proximal tibia fracture, as well as high-grade degenerative osteoarthritis, and overweight patients. These two matched cohorts were compared statistically. Revision for any cause (infection excluded) and revision for tibial loosening were used as the endpoints in the survivorship analysis.

Results : With revision for any cause as the endpoint, survivorship was 95.6% in the SS cohort vs 88.4% in the MLS cohort (p=0.87) at 10 years’ average follow-up (range SS: 2 to 15 years, MLS: 2 to 13 years). With revision for tibial loosening as the endpoint, survivorship at 8 years’ follow-up was 95.6% in the SS cohort vs 100% in the MLS cohort.

Conclusion : HA coating and MLS help to improve alignment and fixation of cementless TKA. This option is a safe solution without increased risk when bone conditions are poor or modified by previous surgery.

Keyword: Cementless Total Knee Arthroplasty; Long Stem; Standard Stem; survivorship at 10 years; TKA in poor bone conditions.

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