Calcium Crystal Deposition in Patients of Knee Osteoarthritis (OA) Using Ultrasonography and Dual Energy Computed Tomography

Abstract

Purpose: Calcium Crystal Deposition is common in OA knee. This study looked for Calcium crystal deposition in Osteoarthritis knee by different methodologies which included Dual Energy Computed Tomography, Ultrasonography, Digital X-ray and Synovial fluid examination by Polarized light microscopy. Methods: 32 patients of knee OA Kellgren and Lawrence grade II and III (Sex ratio F = 21 M = 11, mean age 59.9, Range 43–76 years, mean BMI 26.7, Range BMI 16.9–40.1)were enrolled in this study. Patients with Synovial Chondromatosis were excluded. X-ray of knees was done in weight bearing position. Ultrasonography of knee joints was done by using multifrequency linear array transducer on Logiq E, GE Medical Systems Ultrasound, B mode gray scale with dynamic range of 40–50 dB, GS frequency of 11–13 MHz and GS gain of 60 dB. Knee joint was kept in maximum flexion for femoral condyle cartilage and 45 degree flexion for menisci, patellar tendon, collateral ligaments and supra patellar soft tissues. Presence of hyperechoic aggregates, intra cartilage calcifications were looked for in above mentioned sites. Femoral condylar cartilage was also looked for presence of Double / Triple contour sign. Synovial effusion was tapped in 9 patients for microscopic examination by polarized light microscopy for CPP crystals. 17 patients agreed for Dual energy computed tomography (DECT) and their right Knees were scanned for any calcifications in the joint other than the bones and Osteophytes. Results: Of X-rays of knees of 32 patients, 32 (100%) showed osteophytes, 14 (43.8%) cartilage calcification, 5 (15.6%) meniscal calcification, 16 (50%) soft tissue calcification, 1 (3.1%) blood vessel calcification, 27 (82.3%) joint space narrowing and 2 (6.3%) erosions. Ultrasonograpic finding showed osteophytes in 30 (93.8%), cartilage calcification in 24 (75%) (Double / triple contour sign in 5 (15.6%)), meniscal calcification in 30 (93.8%) soft tissue calcifications in 3 (9.4%) and erosions in 14 (43.8%). DECT images of 17 patients were observed in 17 knees in 25 sub regions and showed calcification within and around the tibio-femoral and patello-femoral joints in 15 (88.2%) knees. 41.2% had hyaline cartilage, 78.6% cruciate ligaments, 23.5% medial collateral ligament and 5.9% joint capsule calcifications. Nine patients had inflammation in the knee joint. These patients were subjected to Synovial Fluid aspiration. 4 out of these 9 showed presence of CPP crystals. Out of these 9 patients, 4 patients had meniscal calcification, 8 patients had cruciate ligament calcification, all 9 patients had cartilage calcification, and none had capsule calcification. Conclusions: Nearly all patients with KL grade II/III knee OA had calcium deposits in the knee. DECT is a more useful tool for describing calcium crystal deposition in the knee as compared to X-ray, ultrasonography and synovial fluid examination. Calcium crystal deposition by DECT was seen in 15 (88.2%) patients. All modalities are complementary to each other. While USG was better than X-Rays to show Meniscal and Cartilage calcifications DECT was particularly useful to detect Cruciate Ligament Calcifications.