Background Placement of a total knee arthroplasty (TKA) in case of end-stage knee osteoarthritis (OA) in young patients is less successful than in elderly, with high revisions rates later in life (1). Recently knee joint distraction (KJD) showed results of clinical improvement and tissue structure modification in patients with knee OA (2) postponing a TKA. The duration of these beneficial effects is yet unclear.
Objectives We evaluated whether the clinical improvement and tissue structure modification in knee OA sustain and persist on MRI and X-rays 5 years after distraction.
Methods Patients (n=20; <60yrs) with tibio-femoral OA who were resistant to conservative therapy and eligible for TKA, were treated with 8 weeks of KJD by use of an external fixator. Clinical evaluation was performed by WOMAC, VAS pain and survival of the knee joint. Changes in cartilage thickness were quantified by MRI, and change in joint space width (JSW) was evaluated on standardized semi-flexed X-rays. The five-year changes after KJD were evaluated and were compared with the natural progression rate of OA in OsteoArthritis-Initiative participants with similar baseline characteristics.
Results From 20 patients (age 49±6 yrs), two withdrew informed consent and three other patients were treated with TKP (after three and four years), so the survival of the knee joint was 80% at 5 years. Moreover, there was persistent clinical improvement compared to baseline sustaining over time: Δ WOMAC +21,1 points (CI:8,9-33,3; p=0.002), Δ VAS pain -27,6mm (CI:-13,3-42,0; p<0.001).
In addition, minimum radiographic JSW was increased at five years as compared to pre-treatment values: Δ+0,43mm (CI:0,02-0,84; p=0.040). Taking natural loss of cartilage thickness into account, this change was significantly different from the changes as a result of extrapolated natural progression (Δ-0,39mm and Δ-0,18mm, respectively) resulting at 5 years in a difference of +0,65mm (CI:0,07-1,23; p=0.031) and of +0,41mm (CI:0,07-0,74; p=0.020) for mean JSW on X-ray and average cartilage thickness on MRI, respectively.
Conclusions In young OA patients, TKA can be postponed for at least five years in 80% of the patients. KJD treatment results in persistent clinical benefit and an increase in cartilage thickness and JSW.
The effects were not as strong as observed 1 and 2 years after treatment, still they represented a significant structural benefit compared to the natural course of the disease. Joint distraction has great potential to effectively postpone TKA and as such represents a promising therapeutic option for young patients with severe knee OA.
Julin J, Jamsen E, Puolakka T,et al. Younger age increases the risk of early prosthesis failure following primary total knee replacement for osteoarthritis. A follow-up study of 32,019 total knee replacements in the Finnish Arthroplasty Register. Acta orthopaedica. 2010;81(4):413-9.
Wiegant K, van Roermund PM, et al. Sustained clinical and structural benefit after joint distraction in the treatment of severe knee osteoarthritis. Osteoarthritis and cartilage/OARS, Osteoarthritis Research Society. 2013 Nov;21(11):1660-7. PubMed PMID: 23954704.
Acknowledgements This study was supported by the Dutch Arthritis Foundation.
Disclosure of Interest None declared