Long-term benefit and survival of knee joint distraction as treatment of severe knee osteoarthritis

Abstract

Purpose: In relatively young patients with end-stage knee osteoarthritis (OA), total knee arthroplasty (TKA) comes with the risk of future revision surgery. Knee joint distraction (KJD) is joint preserving surgery, which has been shown to provide clinical and structural improvement for at least five years. The aim of this study was to evaluate long-term clinical and structural results and identify characteristics predicting survival of the native knee joint. Methods: Patients (n = 20; age <60 years) with end-stage tibiofemoral OA indicated for TKA were treated with KJD. WOMAC questionnaires (100 being best) and VAS pain scores (0 being best) were used for clinical evaluation before treatment (baseline) and every year after treatment, up to nine years. The minimum and mean joint space width (JSW) were measured using KIDA software on standardized radiographs to evaluate structural changes at baseline and one, two, five and seven years after treatment. Survival after treatment was analyzed using the Kaplan-Meier estimator, where failure was defined by TKA. Paired t-tests were used to evaluate clinical and structural changes compared to baseline for survivors and non-survivors. Nine-year survival of KJD was predicted using logistic regression analyses. Results: Three patients withdrew consent during follow-up. Nine years after treatment, survival was 48% and survivors reported clinical improvement compared to baseline: ΔWOMAC +29.9 points (95%CI +16.9 to +42.9; P = 0.001; Fig. 1A), ΔVAS -46.8 mm (95%CI −31.6 to −61.9; P<0.001). Survivors showed a significant remained increase of the minimum JSW (+0.62 mm; 95%CI +0.13 to +1.11; P = 0.020; Fig. 1B) and non-significant increase in mean JSW (+0.31; 95%CI −0.91 to +1.55; P = 0.562) after seven years. In patients whose treatment failed, last reported clinical scores were still improved compared to baseline: ΔWOMAC +20.5 points (95%CI −1.8 to +42.8; P = 0.067; Fig. 1A), ΔVAS −25.4 mm (95%CI −3.2 to −47.7; P = 0.030). At last measurement, the minimum JSW was still significantly increased (+0.37; 95%CI +0.02 to +0.73; P = 0.042; Fig. 1B) while the mean JSW was similar compared to baseline (−0.06; 95%CI −0.85 to +0.72; P = 0.854). Survival analysis showed a difference in survival percentage nine years after treatment for gender (women 14%, men 70%; P = 0.035; Fig. 2A) and for amount of increase in minimum JSW in the first year after treatment (<0.5 mm increase 0%, >0.5 mm increase 72%; P = 0.002; Fig. 2B). Gender and increase in minimum JSW after one year were shown to predict survival of the native knee joint after nine years. Conclusions: Long-term results of joint distraction for end-stage knee OA show long-lasting clinical and structural improvement with a survival of 48% after nine years of follow-up. The last reported clinical scores in patients failing treatment were still improved compared to baseline and cannot fully explain the subsequent TKA surgery. Positive predicting factors for survival of the native knee after nine years are male gender and a larger initial increase in minimum joint space width. The differences between genders may relate to different subchondral bone characteristics between men and (postmenopausal) women.View Large Image Figure ViewerDownload Hi-res image Download (PPT)