The Reliability And Distribution Of Foot Osteoarthritis Assessed By Ultrasound And Clinical Examination In A Hand Osteoarthritis Cohort

Purpose: Foot osteoarthritis (OA) is a disabling and painful disease with similar prevalence to knee OA. To date, foot OA has been largely ignored in the OA research society. There are guidelines regarding the diagnosis of hand and knee OA, but no such recommendations are available for foot OA. Clinical markers of foot posture, range of motion, inspection and palpation have shown limited ability to discriminate persons with and without radiographic OA in the midfoot. Ultrasound may be a useful tool for the assessment of OA features in the foot. Recently, the OMERACT Ultrasound Task Force proposed definitions of inflammatory and structural lesions in the foot, but more research is needed before ultrasound can be recommended for the assessment of structural features in the foot. No studies have explored the frequency of joint involvement using ultrasound in comparison to clinical examination. Hence, the aims of the current study were to compare reliability and distribution of ultrasound-detected and clinical features of foot OA. Methods: The Nor-Hand study is an observational cohort where 300 patients with hand OA (89% women, median (IQR) 61 (57-66) years old) were recruited. The current analyses include cross-sectional data from the baseline examination. A trained medical student (CMF) performed the ultrasound examination of the feet using a General Electric (GE) Logic E9 ultrasound machine with a 6-15Mz probe. The bilateral tibiotalar, talonavicular, 1st and 2nd to 3rd naviculocuneiform, 1st to 4th tarsometatarsal (TMT), 1st metatarsalphalangeal (MTP), 1st interphalangeal (IP), lateral subtalar, medial subtalar and the calcaneocuboid joints were scored for the presence of grey-scale synovitis, power Doppler signals and osteophytes on 0-3 semi-quantitative scales (0=no, 1=mild, 2=moderate, and 3=severe pathology). Ten patients were also examined by a rheumatologist with extensive ultrasound experience (HBH) to evaluate the inter-observer reliability. An experienced rheumatologist (BSC) examined the bilateral tibiotalar, talonavicular, 1st and 2nd naviculocuneiform, 1st to 4th TMT, 1st MTP and subtalar joints for the absence/presence of soft tissue swelling and bony enlargement. A rheumatology fellow performed the joint evaluation if BSC was not available. Ten patients were examined by both the experienced rheumatologist and the rheumatology fellow to evaluate inter-observer reliability. We calculated the inter-observer reliability for ultrasound and clinical examination in all foot joints using prevalence and bias adjusted kappa (PABAK) values due to low frequency of OA in many foot joints. We then compared the pattern of OA features in individual foot joints in the left and right foot by ultrasound and the frequency of sonographic joint involvement in comparison to clinical examination using Chi square tests. Results: Good to excellent inter-observer reliability by PABAK was observed for all ultrasound features (grey-scale synovitis: 0.78; osteophytes: 0.82; power-Doppler activity: 0.98). Similar good inter-observer reliability was found for clinical assessment of the foot with PABAK values ranging from moderate to excellent (bony enlargement: 0.90, soft tissue swelling: 0.99). By ultrasound, OA was most prevalent in the MTP1, IP1, talonavicular and subtalar joints (Table 1). Overall, osteophytes and synovitis were numerically more prevalent in the right foot compared to the left foot (Table 1). Clinical bony enlargement was most common in MTP1 and TMT1-2. Clinical soft tissue swelling was uncommon in all joints with the highest prevalence in the MTP1 joints. Ultrasound-detected osteophytes and grey scale synovitis were more common than clinically observed bony enlargement and soft tissue swelling in most foot/ankle joints (Table 2). In the MTP1 joints, clinical examination detected more frequent bony enlargement, whereas ultrasound was more sensitive in the detection of synovitis (both grey-scale synovitis and power Doppler activity) in comparison with soft tissue swelling by clinical examination. Conclusions: We found good inter-reader reliability for ultrasonographic and clinical examination of OA features in patients with foot OA. Ultrasonographic features of OA were more prevalent in the right than left foot, and most frequent in the MTP1, IP1 and talonavicular joints. In most individual foot joints, ultrasound detected more osteophytes than clinical examination found bony enlargements. The high prevalence of synovitis in the MTP1 joint may reflect normal increased effusion in this joint.View Large Image Figure ViewerDownload Hi-res image Download (PPT)