Change of cartilage T2 in contralateral hip joint after total hip arthroplasty

Abstract

Purpose: Disruption or alteration of the cartilage matrix such as a decrease in the concentration of proteoglycan and an increase in water content is found histologically in early changes of osteoarthritis mapping of the articular cartilage T2 is one technique in joint magnetic resonance imaging (MRI) that elucidates degenerative changes associated with changes in water contents and damage to the collagen network. It is unknown how total hip arthroplasty of one side of hip joints could reduce load applied on that cartilage of the other side of them. The purpose of this study was to evaluate those changes in cartilage T2 values of contralateral hip joint after total hip arthroplasty. Methods: 10 consecutive patients (10 hips), who had previously been diagnosed osteoarthritis in one side of their hip joints, were included in this study. There were all female patients (mean age, 58 years; range 48–72 years). All patients were followed up longitudinally, and MRI of both hip joints were performed before total hip arthroplasty and three months after the surgery. Each subjects’ hip was imaged using an multi-slice multi-echo (MSME) T2 mapping technique on a 1.5T MR imaging system (Siemens Healthcare, Erlangen, Germany) in the sagittal plane with the subject lying supine. ROIs were drawn manually by an experienced orthopaedic surgeon in the weight-bearing area on the acetabular and femoral cartilage. Central medial, as well as central lateral slices, were evaluated in each subject. Mean, standard deviation, and pixel count were recorded and statistically analyzed by t-test. Results: T2 values in contralateral hip cartilage exhibited a significant increase in the lateral ROI of the acetabular cartilage (54.8ms±7.5 → 59.6ms±6.2, p< 0.05), and a significant increase in the lateral ROI of the femoral cartilage (51.6ms±7.4 → 56.4.5ms±7.5, p< 0.05). On the other hand, T2 values in contralateral hip cartilage didn’t exhibit a significant increase in the medial ROI of the acetabular and femoral cartilage. Conclusions: While performing daily activities such as standing or walking, the articular cartilage in the hip joint is subjected to substantial external loading, which leads to cartilage deformation along with alteration in the collagen architecture or water distribution within the cartilage. Among all MRI parameters, cartilage T2 mapping of cartilage is influenced by water content and collagen fiber orientation of cartilage and is indicated as a potent quantitative index for the load response of the articular cartilage. Our results indicated that total hip arthroplasty in one side of the hip joint reduced static loading on the cartilage in the other side of hip joint by the assessment of cartilage T2 mapping in the lateral ROI on both acetabular and femoral cartilage. It may provide more sensitive and detailed assessment of degenerative pathological changes and load-bearing function of the cartilage.