Reproducibility and sensitivity to change of various methods to measure joint space width in osteoarthritis of the hip: a double reading of three different radiographic views taken with a three-year interval

Osteoarthritis (OA) is the most common rheumatic disease, and is becoming a major public health problem with the ageing of the population and the growing incidence of obesity in developed countries [1]. Treatment aims both to reduce symptom severity and to prevent or slow down disease progression and activity. Many symptom-modifying therapies have been proposed with various levels of evidence (for a recent review, see Zhang and coworkers [2]). However, we still lack a disease-modifying therapy because there is no treatment with proven efficacy in preventing, stopping, or retarding the disease process [2]. The structural process in OA affects cartilage, which is decreased in quality and thickness. Other structures may be involved in the damage observed in OA, including subchondral bone, articular capsule, synovium, meniscus and soft periarticular tissues. Hip OA is very common. It affects about 10% of the general population aged 65–74 years [3]. The prevalence of symptomatic hip OA increases dramatically with age.Several trials have been conducted to identify structure-modifying drugs in hip OA, but as yet no such agent has exhibited convincing efficacy in this regard. The structural progression of OA is currently assessed on plain radiographic views by measuring the joint space width (JSW) and joint space narrowing (JSN) over a period of time [4]. This assessment is at present based on chondrometry, as described by Lequesne [5-7]. Other methods have been proposed, such as digitalized chondrometry (i.e. measurement of JSW or joint space surface with computer assistance [8]). Good reliability and sensitivity have been demonstrated for both methods [9,10]. At present, manual chondrometry – measurement of JSW at the narrowest point using a 1/10 mm graduated magnifying glass – performed by trained readers is the most commonly used technique. It has been shown to be sensitive to change and able to detect minor changes such as 0.5 mm over a one or two year period [11,12].R